The cost of batteries is biggest drawback to the n/rboxes that I have found. Ive yet to switch to rechargables, because im paranoid about the reliabilty of them. Instead, I order them off the net, prices are WAY cheaper than in any store for duracells.
PM me if you want the website I order off. It took me a bit to find an online store with brand namesm but havent had any issues as of yet.