I have a VERY fast machine, Core2Duo 2.6 GHZ with 4GB RAM. Even on my machine, I frequently notice that the editor becomes very slow, it sometimes takes about .5 sec after a keystroke until a character displays. This is even true with the newest build, #913. It only happens after pronlonged work and vanishes after a while. The behaviour stops if I disable R# completely, however, it doesn't stop when I just disable Code Analysis.
I ran sysinternal's process monitor while typing in the Visual Studio Editor and filtered for "resharper" in the path. I noticed that Resharper keeps quering the Registry extremely often. Specifically it queries nodes beginning with "ReSharper_OccurenceBrowser" about 1000 times every second. The result is always "NAME_NOT_FOUND". I believe this behaviour might be responsible for a major slowdown, since querying the registry that often is certainly not very fast. Perhaps this is a possiblity to improve responsiveness?
Also see the attached screenshot of process monitor. Especially look at the "Time Of Day" column where you can see that the frequency of those registry queries are very high.