I use an older *istDL which also uses AA batteries - I like them better than proprietary batteries for at least 1 reason - they are the same as the ones in my flash - I only have to keep 1 kind of battery around
I use the Sanyo Eneloops for the most part now - I can get easily 1000 shots on 1 charge. With standard NiMH I was getting around 600. With non-rechargable Energizer e2 Lithiums I've gotten close to 2000 shots.
The only downside I've seen so far is its hard to do a speed change - takes a bit of time to change 4 batteries... otherwise, I love it