Twixtor
 

I remember someone out there saying they use Twixtor for 24p slowmo. Whoever you are (sorry, can't remember) did you buy twixtor or twixtor pro?
What are the render times like on your system?
How steep is the learning curve?

Learning curve isn't very nice. There are some tutorial videos on the Revisionfx site that help. It's important to understand what settings do what to your video. I have the Pro version but either one works rather nicely. The Pro version just gives you more options to deal with. I've had good results out of the standard version. Render times are fairly slow. Depends on how quick your machine is. I'd say for a 30 second clip to expect a few minutes of rendering. It has to analyze each frame to interpolate the next one, and it's pretty processor intensive.

Mike pretty much summed things up.

The big issue are the render times. (Which isn't bad in itself because I think slomo is way overused anyway).

I've also noticed that Twixtor sometimes gets "lost" and won't render some of the starting frames or a few at the end. Never understood it. I finally ended up just rendering standalone portions of what I needed giving it a few more frames at the beginning and end, then exporting them as uncompressed footage and finally importing the clips back into my NLE (where I would trim if I needed to).

You're probably referring to this thread where we drooled over Joe Simon's footage. He said he used plain Twixtor, not the pro.