Most "serious" users are now uninstalling ReSharper. Visual Studio 2015 adds most of ReSharper's key perks and JetBrains has done little or nothing to resolve ReSharper's laggy/hoggy/unstable code (and has said they aren't going to re-write it for Roslyn).

Honestly back in VS 2010 I'd call ReSharper a core tool. In VS 2015, eww.

I've never liked ReSharper, have felt that the "advice" it offers is often over-rated and seems commonly to be wrong for C# (not unexpected given that JetBrains primarily focuses on Java outside of ReSharper, I feel like ReSharper is a Java developer's approach to C#). These days what's baked into VS and the Roslyn compiler platform blows ReSharper out of the water.

Just about everyone I've worked with that had daily complaints about how slow and laggy they felt Visual Studio was didn't seem to understand that ReSharper was 99% of the slow-down, excessive memory use, and UX lag...

I guess I'm not a serious user then because I've never used ReSharper anywhere I've worked.