I don't have any issues with the removable batteries and generally prefer the option to replace just the rechargeable pack/battery rather than the whole controller.
In my experience with the Dualshock 3, the mechanical parts fail way before the internal battery. In every modern gamepad I ever had, after enough use the analogsticks are going to fail somewhat. In my first 360 controller something broke at the base of the stick from constant L3 sprinting in Bad Company 1. My first Dualshock 3's left analogstick is off-center a bit, sometimes registering a minute upward movement in the neutral position (after 5 years and tousands of hours of play) - and the internal battery still holds its load.