I'm implementing an IHttpModule as described in this question. Since we're examining every request, I'm worried there may be a performance hit. Has anyone run into performance issues implementing IHttpModules?
It depends what it's doing...there are so many events in the pipeline that you probably don't know about it's really a "drop in the bucket" situation overall.
If it's does a lot of heavy stuff, it'll have an impact (it'd have to be real heavy...or scale across a lot of hits). If it's something small/light...you won't notice it's there.