With R# 4.0, the editor generally feels sloppier when entering text, compared to the VS editor without R# installed. I think we do have to accept this to a certain degree, since of course R# does much more work than plain VS.
I feel that this sloppiness is generally not much of an issue, since most of the time, when coding, I'm not entering text, but I'm rather choosing something from some intellisense menu. There it doesn't matter much. But where it does matter is, when I'm entering comment texts after //. Usually I key in one or two lines of plain English text without help from any intellisense, and there the slow entering really is an issue.
When I enter text, the characters don't show up immediately as I type them. Instead, nothing happens for perhaps 1 second, and then, the 3 or 4 characters I entered in that second show up all at once. This is a rather "clumsy" feeling.
This behaviour is not there when R# is disabled, so it has something to do with R#.
When I enter a character in a comment line, the Indicator in the right vertical bar (at the top) changes from green to grey for about 2 seconds, thus it reanalyzes the whole code. This happens for every single character. I wonder if R# could be improved in a way that it recognizes that the user is currently editing a comment and keeps its analyzing efforts to a minimum at that time.