Microsoft recently released rollup 3 for Microsoft CRM 4.0 and 3.0. The rollup is a cumulative set of updates meaning it has all the fixes of rollup 1 and 2 plus some additional fixes.
One major fix that was in rollup 2 was the fix for the Notes screen. Notes on almost any record would sometimes hang and the record would have to be closed and reopened to resolve the issue. This issue really hurt productivity and frustrated users, but it is fixed.
We installed rollup 3 recently and had no issues. As always it is important to backup your data and customizations before installing a rollup.
Microsoft CRM rollup 3 can be found here.