When I override a method (using "override" + Intellisense instead of using the - in my opinion - less elegant Alt+Insert => override members R# feature), the XML docs of the base method will not be copied to the new method. In R# 4.0, at least I get a bubble action which offers to copy the XML doc. But this is not enough. There should be an option to auto-copy comments from the base method.
Also, it would be great to propagate changes in XML comments to inherited methods. This could work in the following way: If XML docs of the base and the overriding method are the same, and I change the XML doc in the base method, all XML docs in the overridden methods should be changed as well.
Please consider this for R# 5.0...
BTW thanks a lot for a stable, fast, and marvellous R# 4.0 release! Back in January I thought that you perhaps wouldn't make it, because your feature-to-do list in JIRA was so long... but you proved otherwise :)