Looks like Richard's next...
GP cells: I assume you mean general purpose, right? I didn't want to clarify that by editing the wiki.
[At least somewhat OT:] I'm quite interested in battery technology in general, and this article was another joy.
There was a fellow at the MIT Flea Mkt. last year who used to work at Duracell R & D; said that the biggest problem in battery tech (referring to sealed cells) is the seals.
Fwiw, at the local Radio Shack, they had Li thionyl chloride cells for sale. Not cheap, but I don't want to be nearby when some goofus open up one of those!
-- nicabod, Nick Bodley 20080610 19:20