Yeah, this happens to me as well. ReSharper caches a lot of stuff, and with the size of our solution, the memory consumption on VS is crazy. This usually leads to a forced restart so that VS acts normally again.
They don't seem to have fixed much at all, it's still a total dog - massive memory hog, lots of random lock-ups and crashes. The classic is the pop-up telling you it's working on showing you a pop-up. And even introduced new issues (like including files from gitignore in the change-sets). I'm this close (holding fingers very close together) to just dumping the thing for a text editor. VS2015 has been a total car crash as far as I'm concerned.
I use Resharper and don't get this issue (didn't get it on Update 1 either) - if the project file is updated, VS will tell me that the project file is updated and ask me if I want to reload the project.