I've been using ReSharper now for about one and a half weeks. Now that I am writing some new code, I have more to share.
The most helpful and time saving feature that I have encountered so far is code generation. In one case, I had added a couple of new properties to one of my entity objects. In actuality, I add the code in my test first. R# quickly recognized that the property didn't exist and gave me the option to create a field or property. I chose the property option and presto, R# found my class and added the property. It can do this with interfaces to. This makes TDD that much easier.
I also started using the refactoring tools more as well, and they are very impressive. I have used Refactor!Pro in the past. One of the things I like about R!Pro was that it would let you chose where you want to place a newly extracted method. I haven't seen that yet in R#. Perhaps it's an option somewhere.
I still occasionally see some ASP.Net issues with resolving control references, but I basically ignore the red text and I modified the R# options to use VS intellisense instead of R#. Then at least, I can get Intellisense even when R# thinks (incorrectly) that there is an error.