Yep......it's consistently about 5 hours and 55 minutes on a full PSP charge. As soon as I unplug the adapter it flips to 6 hours exactly. I charge it every 2 days.
My PSP has spent the most time playing Untold Legends and Ridge Racer while unsupported by the adapter. It has only ever drained all the way to dead on me twice. I've never watched a movie without the adapter plugged in. I like it that way because when you play with the adapter plugged in, you get an additional 4th brightness mode on the PSP that you don't get without it. The sound equalizer works better as well. I've never been online or ad hoc with it either.
Mine is a launch unit Gretzky Pack, updated to 2.0......or I should say that it WAS, because I traded it in last night for a Mario Kart DS unit.