Really, downtime isn't a big deal (to an extent, of course) because most people realize that "shit happens" and there will be the occasional downtime regardless of who's handling mail.
The problem is that you are, in effect, helpless in these situations. Like you mentioned, you can at least keep your customers updated when it's a problem with your own machines. When you've outsourced it to someone else, you're at their mercy, so to speak.
"What's wrong with the mail system?" "I dunno." "When do you think it will be fixed?" "I dunno." "Today? Tomorrow? Next week?" "I dunno."
1. Google will bring it back up in a timeframe that is very comparable (if not better) than your average in-house IT team would.
2. Given (1), if you ask people how much per year they are willing to pay for transparency in such circumstances, most businesses will not be willing to dedicate very much of their budget towards it unless it increases reliability. The "helpless" feeling is just because you can't see Google's engineers working to fix it. Surely no one doubts that they are doing their utmost to bring it back.
Back then I could say we are about 75% back and give a full description of the issue in laymans terms which usually curbed the anxieties. Today I basically pointed them to the status page saying that this is all I have to work with. In my experience Google's support has been pretty bad but that is because most of the time their products work well, but yea I feel in the dark when something like this occurs. Still their uptime has been better than having that "oh shit" moment because a DC is degraded.
In the end, everyone could still access the email and nothing was lost.
So...nothing.
All they really can do is tell you "It's down. We're aware of the issue. We're actively working to resolve it."
I argued up and DOWN with people about us switching to google apps for our email.
Up until recently, we were hosting our own mail on a server in our switch room.
"It's more reliable!" I would insist.
Well...it hasn't been more reliable. There has been more than one longish-term downtime that I can remember since we switched over.
When I was hosting it myself, I could give people status updates, an estimate for when it would be fixed, some kind of explanation.
Now, all I can give them is "it's broken. I don't know why, and google isn't telling anybody why."
Very frustrating, especially considering how much we pay every month for it.