Got an untethered iPhone 4 running iOS 5.0.1. Feel free to update.
Of course, if you want to SIM unlock, don't update using Apple's original FW nor update OTA.
This is great news! We strongly recommend that everyone use iFaith or TinyUmbrella to save their iOS 5.0.1 SHSH Blobs.
You can find instructions on how to do that here: Windows, Mac