A123 cells or M1 are proven to be less hazardous, though as you pointed out that LiPo is also safe but some precautions specially the LVC. Now, I am not an expert but here is one or make that 3 type of typical abuse on battery, read the anecdote part:
http://slkelectronics.com/DeWalt/index.htm
To be honest, I think Lipo still have a lot of potential but A123 has them also with a lot less things to take care of. Thats what made me decide. Sorta like almost as good as lipo but needs to take care of it like NiMH (its a bit extreme to say but you get the idea)