Which one do you use? It looks like they have a number of options.. The rechargeable looks like it would be nice until that one time you need it and have to recharge it first.. AA's might be nice for a quick replacement. I would probably use it in a Nalgene bottle, is this a "size matters" situation where you would want a longer probe or just stir it longer? I don't see the traveler mini being very effective in a liter bottle.
I've been thinking of making a trip to REI (or wherever) with my water bottles in hand, because I've had the same question. A NEW smaller model with solar charger is supposed to come out in Jan...