IMHO I prefer CodeRush
The VS2010 version is out now … Very stable,very performant.
Update: CodeRush also appears to be cheaper. R#r commercial license appears to be $349 where as CodeRush is $249 dropping to $99 on renewal
All that said, this is a very personal decision. It will depend very much on what you are after.
The following is a link to another answer I gave regarding things to consider when making the decision between tools like this.
Comparing developer productivity tools