I have always used the eneloop by Sanyo, AA Nihm rechargeable. Never had any problems. The Lithium AA's also work, but still tend to be used up pretty quickly, at least in my usage. I have used this solution in my 2.5 year old DF and the AFDIII before it. Most days I needed 2 sets to make through a full day. I never had any issues with the 28mm, 35mm, 45mm, 80mm, 50mm Shift, 105-210, 210mm or the 150D.
There was a firmware upgrade as I recall to the DF that allowed it to work better with the Nihm batteries. Before this upgrade the camera did not give a very good warning before the power was too low. Also the Eneloops hold a very good power curve.
Best Charger is the Maha 8 cell. It will charge up a set of 8 in about 10 minutes or less.
Since I moved to a Tech camera in late 2011, I still use the DF for occasional testing and keep a set of the eneloops in the camera at all times since the shutter won't close without power.
Not saying Li is bad, just saying rechargeable AA of the right brand work fine. I am still using the same eneloops from 2 years ago. I condition them once every 3 months or so in the Maha charger. I also use them in my D800 Grip pretty much daily and never have had any issues.