Since the release of iOS4, many iPod Touch users have upgraded to the new OS since it adds extra features like wallpapers on the homescreen and multi-tasking.

However many users are now reporting problems with OS which causes battery life to last a short period of time even in standbymode. Many users have reported that the iPod now looses most of its battery life within a matter of 12 hours or so.

"My iPod Touch (2nd gen) is completely charged when I go to bed, but when I wake up in the morning it is completely drained and non-responsive.This never happened under pre-iOS 4 releases."

Absolutely the same with my 3rd gen iPod. Go to sleep with nearly full battery, wake up with a nearly empty one. This update has crippled my iPod. I really hope the restore feature works to get me back to os3..... My iPod clearly isn't going into standby like it used to.

In light of these problems, its safe to say, 2G and 3G iPod Touch users should hold back from upgrading to iOS4 until Apple figures out what the issue is and releases a fix.

Source