Apple is swift in releasing an update which is supposedly made to counter the Untethered iOS 4.3.1 jailbreak, As usual it is recommended that people with jailbroken iDevices stay clear of this update until a untethered jailbreak of this iOS is out, although according to BoyGeniusReport
It’s said to include a few enhancements, address security issues, and it will also fix several bugs that have affected users.
So aside from these features there isn't any thing new to be really excited about, such as iOS 4.3.1 bringing multitasking gestures with iOS 4.3.1 to the iPad / iPad 2 (And iPhone / iPod touch with a few other applications)
So unless you guys are real update freaks and were expecting something new in this I am sorry to disappoint you. Unless one of the "few enhancements" mentioned is a new feature but otherwise this is your ordinary kill your jailbreak update.