My company is evaluating resharper, and it and VA don't seem to play nicely together (both try to present drop-downs etc.).
For the record, I've been using VA for almost 10 years, and after trying R# for a couple days I much prefer VA. In the end I will probably use their code analysis feature, but otherwise keep it turned off.
I do about 75% of my work in C++ still, and VA will still have to be used there.
This makes sense. VA should be usable along side ReSharper, but there is definitely some overlap, and possible competition. Telling VA to ignore .cs files should fix this problem.