If you’re using a jailbreak like ultrasn0w or redsn0w on your iPhone,then it will be better for you to stay away from the iOS 4.1 beta 2, as it patches the exploit used for unlocking it.
(This includes all generations of iPhones-3G,4G,etc.)

And what about the Dev-Team!. We are pretty sure they are working on it.

MYP Advice:Stay away from it till a new and updated jailbreak arrives.