Manually killing background apps wont make a difference - they will be killed anyway, to keep the foreground app running.
Not in my experience.
With the iphone 4 when trying to use Naips, it hangs. Kill off hibernating apps manually and the Naips responds. So I am not sure the auto kill off is 100% effective.
Seen it many times now so can you explain this? I am not the only one to see the same things.