I still experience slowdowns and 100 % cpu usages by devenv.exe after some run/debug cycles, using R# 5.1.1723 and VS2008. This problem has been there in 5.0 since a long time.
I have made some snapshots with dotTrace 4 (one right after the start of VS, where everything is fast), and after 2 hours work and several edit => debug / edit&continue => stop cycles.
Can I upload them somewhere? Your ftp site (ftp.intellij.net) seems to need a user name/password.