depends on your usage. i use enough batteries to warrant NiMH, but i don't use them fast enough to warrant normal NiMH. After years of messing with normal NiMH, i went for the low self discharge (LSD) NiMH and i never looked back.

LSD NiMH are very usefull in equipment, which won't use up the batteries in a few days. I also love to use them in mine camera, because i don't charge mine batteries all the time. I love the fact that mine camera will have enough power, even though i have not chargerd the batteries for weeks.

get a proper charger like the MAHA or LaCross to squeeze the most out of the batteries. Don't cheap out on the chargers, even if you can't afford a MAHA or Lacross, find one which has independ charging bays.

Batteries to avoid are those who are to good to be true. Some cheap AA NiMH batteries have wrappers with "3200 Mah" on them, they are not. Impossible high battery ratings, usually means they are junk.

Also avoid 2700Mah if you don't want high self discharge rates.

NiCa batteries are also a bad choice as rechargable AA's. (although they can be usefull in some applications)

Don't mix in Li-ion's in to the mix, unless you have great knowlegde about them. Uncarefull use of Li-ion can be dangerous and due to the much higher voltage, they can fry your equipment.