Right in time for iPhone 3.1, the iPhone Dev-Team has begun issuing their usual warnings about jailbreak/unlock users and new firmware updates:

ultrasn0w users must stay away from official 3.1 (incl. betas) until we release the tools for it, or you'll lose unlock!

Tempting as a tasty new beta may be, if you can't live without your hacked iPhone, don't hit that update button now, or any time before the iPhone Dev-Team has new, tested tools ready for you.

Once again, you've been warned!