http://www.macrumors.com/2008/08/12/two-weeks-later-mobile-mes-uptime-calculated-96/

Two weeks after Apple announced that all MobileMe systems were up and operational after a rocky transition, there continue to be sporadic reports around the web of various service outages inclusive of a 4.5 hour mail outage yesterday. But has MobileMe gotten more reliable?

According to Apple's MobileMe status history, there have been approximately 13.5 hours of various downtime over the past two weeks (336 hours); that is, MobileMe has a 96% overall uptime over the past two weeks.

Determining whether 96% is good or bad can be subjective to the user. This editor and user of MobileMe has hardly been affected by the outages but other users may have been more affected by the timing or the content of the outages. In general we would consider a consumer-oriented service such as MobileMe to have an uptime of at least 98% which would effectively half the downtime that MobileMe currently experiences.

Walt Mossberg has expressed similar sentiments, saying that currently MobileMe is far too flawed to be reliable.

http://www.apple.com/support/mobileme/system_status_history.html