The only consistent problems have happened to people running VMWare Fusion, software that lets you run Windows on Mac. VMWare's competitor is Parallels, and that has been trouble-free. So if you are using VMWare, wait for them to issue an update before you install Lion 10.7.4.
Those who have not installed Lion at all will find that the version they get from the App Store when they do upgrade will be the most current version with all updates in place. This is an improvement over the old DVD model, where you had to get a disk from the store which was almost always outdated at sale.
The Safari 5.1 problems, specifically the "Webpages not responding" issue is STILL not fixed, as of 5.1.7. Lion users are stuck with it, but Snow Leopard users should stop and stay with version 5.0.5 until this mess is cleaned up. It can be downgraded if you are running 10.6.8 and did get Safari 5.1. You can read about my experience doing it in the April 9 blog posting.
So go ahead, Lion users, get the update. Also be sure to get all Java and Security Updates. Now that we finally have Mac malware to worry about, it's important to keep up.
Last, always Repair Permissions after running Software Update. If you've forgotten how, it's in the November, 2011 Update.