My experience with Android music players on my Samsung Galaxy Tab was hit-and-miss.
I am a big fan of Winamp on the PC platform, but i found the Android version to be a horrible mess, which would more often than not crash on me, come up with lots of playlist errors after every start-up, and in general be more of a nuisance than anything else.
I unistalled Winamp and never looked back.
The thing is, I have a lot of music that's improperly tagged, and way too many music player apps nowadays seem to be fixed on tags for everything, from navigation to playback. This is wrong, in my view.
I'm not a fan of payware, either, so I can't comment on Poweramp.
However, after a lot of trial and error, and going through the likes of MixZing, Cube and so on, I found that MortPlayer is the best music player for me. It can read tags, but is also very capable of playing simple folder structures. If I have a CD ripped to MP3 without tags, all other players will just display "unknown artist" and make a general mess of the playlist, while MortPlayer can simply play any folder I choose, and will use the file and folder names just as happily as anything else. That, to me, is the best feature.
I am not interested in equalizers and DSP - these are easily superseded by a good pair of headphones.
I'm also very much against the idea of a music player being anything more than that. I loathe the iTunes idea and concept, and would not touch any application which attempts to put all my music into a library, categorize it and so on. I prefer to keep control over everything I have, without some genius programmer somewhere deciding how a program should organize my music for me.