MS does supply a product in each category, but most MS dev shops that I have seen will more often than not be using some of: svn instead of Tfs, nUnit instead of MStest, castle or ninject instead of unity, nHibernate instead of EF, etc. And targeting firefox/chrome with jQuery. As far as I know there's no clear leaders in the distributed cache niche, and there is a fair amount of interest in noSQL stores like mongo, couch and ravenDb.

Where the open source choice is more functional, cheaper or just more familiar, it often gets used instead. This is good.