yeah, but for some reason some plugins (like cxmb) lag on my psp, didnt have that problem on 5.50 though.
I have a PSP-2001 w/TA-85v1 mobo also. I had 6.20 pro-b5 installed until recently. My PSP is currently running 6.39ofw/6.39me-4/6.39pro-b6 combo ATM. As far as the laggy cxmb goes, try neur0n's hacked version. Your problem could be the theme you are using, try a different one or set the cpu speeds to 333/166? I have not experienced any lagging in the XMB even with game_categories_light_6.3X.prx installed. Good luck.
I installeed this, much faster than PRO, thanks!