I have a 2 year+ 3660, the battery has gone to hell, and here, from my POV, repairing it doesn't make much sense, money-wise. Add to the fact I'm outside of the US and the shipping on them repair kits make it even worse.
After this experience, I'd really like swappable batteries, but such PDAs are still in the minority in the market (and being quite smitten with the Treo 600, it's certainly a big minus for me
).