For those of you who can solder, you can try replacing the cells in bad packs. My pleo is almost a year and a half old and its battery pack went completely dead. I purchased some AA sized nickel-metal hydride cells and replaced them.
The most difficult part is disassembling the pack. I recommend a Dremel tool with a cut-off wheel. Cut into the short ends of the pack at the separation between the brown top (belly) and green part. There are pegs that are glued in which you'll need to cut through. Once that's done, pull it apart and remove the rotating latch. Remove the two screws under it and the cells can be removed.
Cut away the heat-shrink covering from the cell and take note of the arrangement of the cells and duplicate it with the replacement cell. You'll have to remove the thermistor and put that on the new pack. The contact on the pack adjacent to the positive post is not the negative terminal of the cell above it. It's insulated from it and is connected to the exposed negative terminal via the thermistor.
I bought 2500mAh NiMH cells from batteries.com -
http://www.batteries.com/productprofile.asp?appid=385310Oops. It appears they're out of stock. Look around for NiMH cells with solder tabs.
I'll take some pictures and post more details if there's any interest.
Carl