For anyone who has been stuck with 3.1.3 for the longest time, salvation has arrived in the form of Spirit Jailbreak. It is untethered (ie you do not need to run the software to reboot your device if the battery goes flat).
Found here http://spiritjb.com/
I'm going to wait a while for the developers the iron out the kinks before using on my son's iPod touch, or I may upgrade my own phone to 3.1.3 and JB it again. The untethered feature is quite appealing.
