I got a Biolite for Christmas after lusting after one for some time. As we had more to cook on Christmas Day than possible on the hob, I took the opportunity to try my new toy out. I was impressed by the speed with which I got a boil using sticks and birch bark.
I was also impressed by the rate of charge that my phone managed which was similar to that possible through a socket (perhaps USB being the limiting factor in the latter case).
I found that as the burn chamber is quite small, the dryness of the wood is quite critical - above a certain moisture content the water vapour prevents the secondary ignition (wood gasification?) at the top of the chamber which seems to be what provides a lot of the heat and the smoke reduction. However as the outside of the burn chamber gets quite hot, I think good wood drying discipline would be a beneficial habit and neatly solve this problem - that is, collecting a couple of short sticks for tomorrow, today. I also reckon that getting used to setting a fire within the confines of the chamber will also help. It's a bit weird if you're used to open fires or using a brazier.
All of the individual elements of the Biolite are not particularly innovative - the thermopile is used for fans for wood-burning stoves to circulate heat, the use of a fan to get a hotter burn isn't unprecedented, rocket stove construction for efficiency and emissions reduction has been explored a great deal. However, the cleverness of the Biolite is in combining these elements to get good heat production, low smoke and reduced fuel consumption without needing an additional power source. The ability to charge devices a bit is a plus - not ultra-compelling but certainly with applications - for instance, I don't think it would be that useful for maintaining a smartphone that was on constantly, or a gps unit, Garmin etc, but to keep a phone charged in case of emergencies, topping up head-torches, keeping radios or mp3 players going, it'd be great. It also occurs to me that I can store a much bigger encyclopaedia offline on my smartphone than I can carry on a backwoods trek - so for keeping useful information to hand, it could be very useful!