I have 4x 2000mah and 4x 2100mah RatShack batteries. They suck, but I got them cheap. They last max. 2 hours w/ PP. My Walmart battery lasts a good 4 hours plus. Basically, I use the AAs as a backup in case the Wally dies or gets disconnected...
I'm looking into a love-you-long-time battery system involving 12v 7700mah nicads...
Terry