It seems with most recent fix, powermizer levels are messed up. Maximum performance level is usually 1 (out of 0..4), where 3 and 4 are usually same as level 0.
Also on number of occasions performance levels chanced their values (there were constant with older drivers).
The most important part is fixed - if you select prefer maximum performance - the card enters highest clocks frequency (sometimes it's performance level 4 and sometimes it's performance level 1). Some screenshots describing the problem were reported in this thread: http://www.nvnews.net/vbulletin/showthread.php?t=151568