How do I identify apps or settings that cause performance problems?
Watchdog will monitor your phone's performance and alert you of issues. Here's a quote from the Lifehacker article on Watchdog.


  Watchdog runs in the background,
  watching for apps to start using more
  than a certain percentage of CPU power
  that you specify (with a default of 80
  percent). When it notices an app going
  out of bounds, it notifies you and
  offers options to kill the app, ignore
  it, or add it to your "Whitelist" of
  pay-no-mind programs. By default,
  Watchdog doesn't use much power
  itself, only checking in every two
  minutes or so, but you can make it run
  more real-time if you'd like to really
  pin down a problem you know is
  happening.