Arstechnica points to a new support document which details many changes that Apple has implemented into the MobileMe site in late September. Apple points out that since MobileMe is a server-side service, updates occur transparently to all users of the service:
Apple uncharacteristically details a number of changes which include many performance issues and bug fixes to all services.Since server-side updates are a bit more innocuous than a standard software update to Mac OS X or Microsoft Windows, it's easy not to notice that updates are occurring. Usually the only hint of these updates is that things just "work better"]
MobileMe is the online mail, calender, contact and sync services available to Mac or PC users. MobileMe's initial rollout in July was marred by poor performance, downtime and some data loss.
Article Link: Apple Details Ongoing MobileMe Upgrades