I am posting this because when I was pondering getting the AA battery adapter for my MobilePro 790, I spent forever trying to find any data about how well it worked with NiMH batteries. I couldn't find any information. Now I have bought the MC-BA10 adapter and have had a chance to test it out.
Over the last two days, I have been running my MobilePro on a set of four Energizer 2500 mAh NiMH AA batteries (which have 30-40 cycles on them already). My total run time before the batteries died was 5 hours and 15 minutes!
This is with an Alvarion DS-11.b 5v PCMCIA 802.11b card with power save mode enabled, half screen brightness, and continual heavy usage (tons of IE browsing, some IRC, and some AIM) that kept the CPU churning away for most of the time.
So not only did the AAs work well, they worked better than my lithium-ion battery! The first very low battery warning popped up after 4 hours and 13 minutes and then I was able to run for an hour longer. I hope this post helps anyone else considering the AA adapter. It was well worth the cost.