I've wanted one since it came out, and I already have the Sigma 10-20. So, yeah, both!

Like Mike says, they're different tools for the job. Lots of fisheye shots gets old really fast, but one or two in a group can be outstanding. They're tough to shoot but I've had a little experience with them, and sometimes you need something like that to really get a great shot.

I can't see your example because of my work connection, but I keep getting reminded that it's such a great lens...