Well I got 21015 flashed to my phone, and Ive found the same problems that made me look for lennys or helmis old 19xxx versions.
1.) all music playback stops after about 4 minutes. i havent done the stupid hack that ruins battery life.
2.) my phone wakes up constantly about every 2 minutes(even in the same spot on my desk).
actually the second problem fixes the first , because after the screen has turned on and off for like 3-4 times and playback has been going for like 4+ minutes, it stops. Then after 2 minutes the screen turns on, playback starts...then the screen turns off leaving playback going for another 4 minutes, til playback stops, and screens come on and off and on ..... ........pure awesomeness 
How are people not getting these problems? are they not using their devices(or at least ppc6700) for music?
I havent listened to any music in a month or so, ever since I went from 19xxx to 20931->20748->20755->20924->WM5->20755->21018->21015. I couldnt listen to music on any version(well i could on wm5 but it was ungodly horrible)
3.) When I have the earphones plugged in and I get a call, the phone speaker still rings. I used to be able to just leave earphones plugged in during class and it would pretty much mute any event/sound that triggered, since it routed all audio out to headphones, alarms still get routed to earphones but not a call ringer.(I am using ibliss dialer, maybe next flash I will try a differnet one)
anyone have access to the old helmi or lenny files? before the new stupid modular cluster-f*** buildos
the other aspects of 21015 seem nice, the threaded sms window does not do the annoying close then open the touch keypad, and then close it when i try to click in the input box. and everyting seems a little speedier.