Yesterday, one of my Google Apps for my Domain accounts was down for several hours. It eventually came up but it looks like some other Gmail folks aren't as fortunate. A Google Groups thread has several members complaining that they are receiving 502 errors when trying to access their Gmail accounts. There is a pretty big outcry of how Gmail is not stable enough for them.
Gmail Alerts Manager updated another Google Groups thread with updates, and as of last night, everyone should have their email up and running. However, a number of folks posting in the Google Group are still not able to access their email.
We'll update this post if we get any other reports.
Forum discussion continues at Google Groups.