I had another play with Resharper at work recently. There’s lots I like about it, for example the code suggestions, and the way it grays out unused functions and unused branches in methods. It’s really good for tidying up legacy code. And “Go To Implementation” is a massive time saver.
There’s a few things I don’t like about it. I don’t think it’s Refactoring options are much better than those built into Visual Studio – I only ever use Extract Method anyway. And I don’t like its “Find All References”.
Anyway, when the trial ran out and I uninstalled it, I found I’d lost my Intellisense squiggles (under Syntax errors and the like).
To turn them back on, it’s under Tools –> Options –> C# –> Advanced. Check “Underline errors in the editor” and “Show live semantic errors”.