It's probably not representative, but the first time I tried to install IE7 it went through all the motions but didn't install. I only wanted to see what it's like, being a convinced Firefox addict and very suspicious of MS software.
The second time I tried, I thought the machine had locked up, it took so long. It did in fact install, but only after something like 15 minutes of chuntering disk drive time. The install worked, too! It's a lot slower than Firefox, and gives no indication that it's working - click on a link and nothing happens: no cursor change, no progress bars, etc. Then, when all seems lost, the new page suddenly pops up.
Conclusion: better than IE6, but s l o w. Firefox has it well beat.