I have one and I'm very happy with it.
It takes six AA batteries - but if I'm not mistaken, I think a battery pack was available - but not necessary.
I don't know how rechargables will affect the system. I just buy all my batteries at Costco - and they last a decent amount of time, surprisingly.
I would say the screen is slightly smaller than a GBA, but it is a pretty bright screen. I have never been dissappointed with the colors.