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However, in my limited experience when I was at a dot com with IIS and worked on it a bit myself, I will say that it didn't seem very stable when running large numbers of web sites...though that instability could very well have been the result of the limited experience running web servers in our group.
The big surprise for me was the url rewriting thing. I've looked into it before, but that fix they mentioned sounds easier than the other I read about.
they told me to not compress .js files. I tried that, and it still didn't work, so I uninstalled it. Glad I didn't spendthe $1500 for the program!