Microsoft has released Update Rollup 4 for Exchange 2010 SP1. As always, it is a cumulative update and can be applied straightaway without applying all the previous rollups. Forefront has to be disabled (fscutility /disable) while running the update rollup and enabled afterwards (fscutility /enable).
The setup checks whether the server has been configured to look for certification revocation list and advise to disable it, as the setup will take too long otherwise. Now, that is smart
Download the update rollup 4 here
After the issues with Update Rollup 3, my take will be to test the new rollup thoroughly in a test lab or wait a few days before rolling it into your production servers.