I have the stock battery.
I can pull my phone off of my charger, go to work, work 5-7 hours and not have touched my phone and lose 25-40% of my battery. This is without having even touching the phone. Maybe checking the time, but no apps or anything else. Then it stays off and dormant for hours. As in, not even touched.
I am a fairly heavy user, when using my phone. Texting, web browsing, playing games, fooling with all sorts of stuff. My battery life usually ranges between 3 and 5 hours before it needs juice, depending on just how much I use the phone. When I use the phone very little the battery lasts a little longer. But again, in 5 to 7 hours I can lose a pretty substantial charger while doing nothing. I normally use an app killer to kill apps to attempt to conserve a bit of battery life while it isn't being used. (I understand that the debate rages on over app killers and battery life, but it makes me feel good)
Realistically, my battery life sucks. On a normal day I have to charge it at least once, maybe twice before I even get to bed. Most days it stays plugged into my PC, because the battery life is so weak. This is my only real issue with the phone at all. Something I plan to correct just as soon as Verizon gets around to releasing the 2150mAh battery.