Update #1: PwnageTool and redsn0w have been updated to include a fix for the iPhone3GS/i4 side switch vibration issue (only for 4.3.3!). Thanks to *i0n1c for tracking this down (even though he doesn’t even have an iPhone!).
If you’re already jailbroken at 4.3.3 (by either redsn0w rc15 or custom IPSW), you can install this fix simply by running redsn0w rc16 over your existing 4.3.3 jailbreak. Just uncheck the “Install Cydia” option and check any other options you want. The fix will be installed no matter what you’ve selected. This is safe for even ultrasn0w unlockers to do (because redsn0w itself won’t update your baseband…only an iTunes stock IPSW update/restore will do that).
redsn0w rc16 has a few more improvements: Windows 7 and Vista users should no longer need to set their CPU affinity…just run redsn0w as Administrator in XP compatiblity mode. Also, the “verbose boot” option for old-bootrom iPhone 3GS has been fixed for 4.3.3 (remember: old-bootrom 3GS users can even have custom bootlogos that show right at power-up). Enjoy!

redsn0w 0.9.6rc16: