I LOVE using UWA's!
The images here are from the 17-40. I chose these in particular since they are all shot as wide as possible. I also use my UWA ~2x a week working indoors for a company here in Tulsa. I would, however, really consider your style. My wife rarely ever shoots with my 17-40 on her 60D, she prefers the 35L, that is her style and that is what she uses to get results. The 17-40 was the first L lens we bought and I have grown to love it despite it's flaws. Next year I plan on upgrading to the 16-35, but if you are a fan of the UWA look, I would consider the 16-35, 17-40, or Tamron 17-50 2.8. I have used all three and have few complaints with any of them.
Again, if wide is your style, have some fun, but if not, save your money to later optimize your shooting style.