I use a Tokina 11-16 2.8 MK I and I love it. It is a great all around lens, but it suffers from minor distortion and flare issues. Nothing too significant, but you should know this before buying the lens. I haven't used a Canon 10-22, but people rave about this lens. It is a variable aperture lens, while the Tokina is a constant 2.8. The trade off is 2.8 through the zoom range or an extension of 6mm with nominal distortion/flare, and a variable aperture. I heard that there is less distortion and flare with the 10-22, but I can't confirm this from experience. Although, after viewing some pictures, such claim is apparent!
Honestly, I would stay away from a 16-35 unless you plan to buy full frame camera such as a 5d2 or 5d3, demand absolute sharpness from corner to corner, or require 2.8 for a slew of reasons. I own a 17-40 and it is a good walkabout lens on my 60D, however, it is not a proper substitute as a ultra wide angle lens for a crop body. Neither is a 16-35!
So, I would look at the beloved Tokina 11-16 2.8, Canon 10-22 3.5-4.5, or the thrifty 17-40. Again one can eliminate the 17-40 if one requires an UWA for a crop body. As far as buying a powershot, I would buy an UWA lens and work exclusively with your 60D for now. There are ample tools and options when using a modern dslr. I hope this helps you out!
The photo's recording info:
shot from a tripod, iso 100, shutter speed 1/40, f/8.0, at 11mm, and just a regular raw converted file. The raw file is much darker on a decent wide gamut monitor. I just want to show you how the lens handles multiple colors, deals with over and under exposing, plus show a little distortion. The camera is a 60D. Again, I hope this helps you out! Oh yeah, this is a Florida sunrise from Melbourne Beach. Or in that vicinity!