Did an upgrade for my iPod touch 2G Firmware from ver 3.1.2 to ver iOS 4 on 22 Jun 2010. So far very happy with the performance and some of the new functions although cannot enjoys the multi-tasking.
However, did notice that the mail updating is abit not as responsive as previous version but the airplane mode is a welcome addition for iPod touch!
Anyway, it free so just go ahead to upgrade it. 😉