First, in my opinion, many of the problems people are experiencing are a matter of getting adjusted to the new lens design, and the new way of "working" it. I have a good deal of experience with high-end cameras, as do many XL1 owners, but that doesn't mean there isn't a surprising learning curve with this new lens design. In fact, it may be more demanding because of that experience.
Second, there are things you can do with this lens because of its design that you just can't do (or are, at least, more difficult) with traditional lenses. For example, it is possible to make extremely small focus changes "manually" that would be tougher to pull off "on-line" with a typical lens. For me, this has proven useful when shooting macro such as flowers very close-up. You could use the auto-focus, but I tend to avoid that because of inevitable "hunting."
Also, I've used this capability to good use when shooting other things that were moving, but that didn't deserve the auto-focus. While traditional lenses can give you a slight "bump" when you move the focus ring from a dead stop, proper use of the XL1 lens will never give this, as long as you know that you need to move it very slowly.
Basically, you need to get used to the speed of the focus and zoom ring response. Once I learned those speeds and how the lens responds, I was able to see the advantages of the design, which balance off rather nicely, I think, with the downsides.
The focus ring on the XL1 is inner focus-servo controlled. When you turn the focus ring, there is a slight delay as expected, but when you go past the point where the image is in focus and then turn the ring back, focus may not be where you expect it. Also, you may notice that moving the focus ring slightly has no immediate effect and that continued slow manual turning of the focus ring may cause the focus to remain the same and then at some point speed to catch up.
I think the key word here is "expected!" This lens does not behave as expected. This makes evaluating it at the store or anywhere else problematic. It takes a while to get used to the focus and zoom rings. Having used the camera now for a couple of months, I find that there are benefits to this servo mechanism that a "normal" lens doesn't provide.
As for moving the ring without effect, here's my two cents. When you move the ring very slowly, you're making VERY small adjustements to the focus. If you're looking at an object in the center of the frame with the exposure at, say, f16, then if you make small adjustments to the focus, then you won't notice them! Early on, when I would get frustrated, thinking that it wasn't responding, I would move the focus ring faster, and then BAM, it's WAY out of focus... Basically, you really need to learn how fast to move the ring for different focus/zoom changes. Having developed a better sense of that for myself, I've come to really enjoy it.
For example, with this small adjustment capability, it's much easier to make fine focus adjustments with the ring than with the rocker arm. And you can do it with your little finger while shooting, and not shake the camera the way you might do with a typical lens. You can avoid that little "jump" that can happen when you go from a dead stop to zooming.
I pulled off the road the other day to get a shot of the setting sun. While I was out there, I zoomed way in to a point about a mile and a half down the road (I'm in the mountains). As it got dark, the depth of field narrowed, and I was hand-holding, using the image stabilization and adjusting the manual zoom with my little finger.
I was able to do a very fine focus adjustment to pick out a car in the distance and keep it in focus as it moved toward me. I can't think of another camera I could have pulled this off with without a tripod. For me, this means that there are a lot of shots that I'll be willing to go ahead and get, that I wouldn't have messed with using a higher-end, but heavier (and without good image stabilization) camera/lens combination.
In a nutshell, I appreciate the difficulty people are having with the lens, but my experience is that once you get the hang of it, and learn how to get to the focus point quickly, it actually does some things better than the lenses we've been long accustomed to.
That said, I have had the problem that someone else mentioned recently where the zoom will jitter pretty badly when using the rocker arm, occasionally. The times I've noticed it is when zooming from all the way back, very slowly in. Not always, but once in a while, it will "jump" along, making quantum leaps to the next position, rather than smoothly moving.
I talked to Canon about this, and a customer service rep said they had heard of this before, and wasn't encouraging that they'd be able to do anything about it. This one bothers me. It may be endemic to this speed-sensitive servo, I don't know. As far as the zoom and focus working the way they're supposed to, though, I think it's just a matter of getting used to it.
Now here's a short tip about focus control. If you zoom in on your subject, focus manually then zoom out only to find the subject is out of focus, make sure you weren't in the "easy" mode (green box), which doesn't allow manual focusing. You can turn it, and it might adjust things briefly, but then the auto focus will kick back in immediately.
I just did a little informal time test with my XL1. I pointed the camera out the window, through the screen, and focussed the camera on a leaf a couple of feet away. I zoomed back full wide, and then pointed the camera to the house across the street (their bedroom blinds are closed, by the way).
I started counting to myself, zero, one thousand, one, one thousand... as I zoomed all the way in to the rooftop, focussed manually, and then zoomed back out. I did this several times to account for measurement error. Generally, it took me between 3 1/2 and 4 seconds to do the whole operation. It never took more than 4 seconds. Based on my general memory with the Sony M7 camera that I shot with for three years awhile back, this felt like a similar amount of time. The zoom is a little slower on the XL1, but I felt that I was finding the focus about as quickly. As there wasn't any doubt that I was finding it. I would go back in to check and it was indeed very sharp.
In the process of this little experiment, something occurred to me. I realized that I am putting my thumb on the underside of the lens (directly under the buttons), and the using my third finger to push the focus ring up or down. This provides the leverage needed to push the ring fast enough to GET it there in one swift move, and then have some time for a small (slow) fine adjustment. If you need to do two or three pushes, it can be done quickly with this "thumb-fast" method.
With the thumb on the focus ring, you can't move the thing far enough (or fast enough), and focussing would indeed be a frustrating experience.
When using a Steadicam or similar support device, or doing a snap zoom, I would probably opt to use the auto-focus button in these circumstances. I've used it quite a bit, and though it's sometimes a beat slower than I'd prefer, it's still often faster than focussing manually. And doesn't require that you're even looking at the monitor. If you're following a particular subject in the middle of the screen, then I'd use the auto focus (in good light).
If your XL1 seems to go out of focus at the strangest times, for instance when you know you're in the manual focus mode, well, all I can say is that this kind of thing used to happen to me when I first got the camera. Unless you really nail your hand position, knowing that it's not accidentally hitting the focus ring or the auto-focus button, focus can get changed pretty easily.
Since establishing a workable way of holding the camera, and being familiar with it, I've not noticed this kind of "weird" behavior for a couple of months, now, and I'm doing much more shooting now than early on. I don't think it's because my standards have changed!
Oh, by the way, as for "snap-focus," try the auto-focus button. Works perfectly, in my experience, although you don't have control over the speed at which it will go. In a nutshell, it will be faster than I believe anyone could do it manually with a traditional lens (okay, at least no slower), it won't miss the focus, and it won't cause any camera movement at all.
I hope this is helpful, both to current owners and to those considering the camera. In my view, it's a learning curve thing and, particularly, one that professional videographers aren't used to having to go through.
Scott Barber is "in the biz" at New Context Video Productions in Asheville, North Carolina.