I have never used the 16-35mm but the 24mm F1.4L is a lovely lens with a wide but not super-wide angle of view & of course the F1.4 aperture is brilliant for low light situations
I am very tempted by the all manual Samyang (also sold as Rokinon & Bower) 14mm F2.8 which is a fraction of the price of the Canon 14mm & does get very good reviews Samyang 14mm f/2.8 IF ED UMC Aspherical - Full Format Review / Test Report
Bower 14mm f/2.8 Ultra Wide Angle Manual Focus SLY14MMF28C - B&H

Wow great tip Nigel, looks like a sweet lens. Sharp as sharp gets and minimal CA. Of course it's not rectilinear but would be awesome on a crop sensor (no vignetting and less evident distortion). Glad I sold my Tokina 11-16.

From all that I have seen it is rectilinear although it does have some moustache shaped barrel distortion in the centre which is quite unlike the distorted image that the Samyang 8mm fisheye lens will give. Markus Keinath - Samyang 14 mm / 2.8 IF ED MC Aspherical Test

The 14mm Samyang looks like a good value lens - not sure how you'd go about getting ND or any other filter on it though...

You would need to use a matte box.

I've got two matteboxes - both vignette with a 14mm lens on a 5D. So, if you know of one that will work let me know:)

I bought one of the 14mm f 2.8 Bower several weeks ago and have found it to be a worthwhile investment. For stills it's fantastic, I use PT Lens to correct the moustache distortion.

For video I've found a lot of uses for it but it is limited by no place for a ND filter. I had hoped to tape one over the rear element, but it's convex and sticks out slightly past the mount. A matte box may work. I have several but have had no time to try them and see. I'll try one when things slow down a bit. Still it's a good value if your looking for a wide angle.

cheers

Morton

A while back I got a Century mattebox, and when I later discovered that my 16mm would vignette, I got so friggin' mad that I took my Dremel tool and widened up its opening. Now it works perfectly, (and not too obvious signs of my butchering either ;^)

This is the mattebox I got:
Century DV Matte Box 4x4 System

-- peer

Note that the 16-35 II is definately an improvement over the I, but also has an 82mm filter thread.

Also, not sure this counts as it's more of a medium-wide, but no one has mentioned the 35mm F1.4L yet, it's also a fantastic lens.