I've noticed that at 190 cycles my battery now holds 78% of its original capacity. Under Apple Care I would be eligible for a battery replacement. However, I am reluctant to proceed. The battery is glued to the bottom case, and to replace the battery, I assume that Apple swaps the entire bottom case with a generic one, on which the machine's serial number is missing. That bothers me, especially for resale value. To anybody that has had their battery replaced: am I correct in assuming that the bottom case gets swapped with a generic one?