I believe it, that's why I always press and hold the blackberry (menu) button to see the apps running after I finish using every app (kind of like the Task Manager in Windows). If there are any apps still running which I thought I closed, I close them from here so only the default Blackberry apps are running (messages, phone, home, BB messenger, browser). I do this every time I close an app. My wife's Droid Pro has an app that supposedly closes apps (Advanced Task Killer) but some keep reappearing even when her phone is not in use. I'm glad Blackberry doesn't have that problem (at least I hope it doesn't). By the way, in all my testing I closed all apps this way (in addition I did a battery pull before each test) so the only apps that were running (supposedly) were the default BB ones.
I wanted to update this thread regarding Wi-Fi. I tested it last night. Before I slept I had a 100% battery charge, disabled GPS, disabled Bluetooth (I've actually never had this enabled), but this time I enabled Wi-Fi and connected it to my home wireless router (using WEP key). I left it connected that way overnight and the next day the battery only dropped 5% (the same as if Wi-Fi were not enabled at all). A possible explanation is that since there was no internet browsing going on overnight (and I disabled any apps from accessing the internet on their own automatically), the Wi-Fi didn't eat up any battery power. It's too bad I didn't find the same when GPS was enabled. So in my case I will probably leave Wi-Fi enabled (but definitely keep GPS disabled when not in use).