I ran into a worse problem with my 4G Touch where it would drain the battery badly when in standby. It had nothing to do with multitasking, or bad apps or push. It was a wi-fi drain. I turn on airplane mode and it can go weeks instead of 1 day.
My iPad doesn't drain when in standby but I felt like the battery drain was going faster when I upgraded to 4.2 but I still get around 9 hours. It's usually ~5% per 30 mins for the things I do.