iOS4 is CRAP on my iPod Touch.
Well battery life anyway. Went from 100% to less than 20% in 8 hours, less 10 minutes of checking mail and App store. Wifi was left "on" while sleeping.
The original OS version 2 was way way better. I could leave the thing alone without worrying about battery life. Wifi was also more robust. Now even in line of sight of the transmitter, the reception would drop to 1 curve at times.
I can imagine what the Great Steve's response: "Don't leave Wifi on."