I very much doubt that your experience of overhead is on all of the paths used by Visual Studio. The main issue id going to be the overhead from very large files or (perhaps more likely) from files accessed very frequently. You can turn on detailed information about the files accessed by standard shield
Standard Shield > Customize > Advanced tab > Show detailed info on performed action
(just for a while) to show you the files it is scanning. Then you could selectively exclude the most frequent files and see how the overhead goes.
I don't doubt his experience at all - in fact, it is an experience shared by me and all of the other developers I know who use avast with visual studio.
For the original poster, the advice of watching what is scans is good advice, because you're going to have to exclude a ton of stuff. Starting with your projects directory, then the <windir>\microsoft.net directory as well as the assemblies directory, any iis virtual paths that you're using as well as the directory where .net 2.0 puts the shadow files and precompiled iis files, etc.
Once you finally exclude most of those things, performance should return to normal. Or you could do what I ended up doing, disabling avast when I'm coding and avoiding suspicious internet sites while it's off. I turn it back on when I'm done.
