I've been using the GrandCentral service for about two months now. I absolutely love the concept. Being able to move my phone number around, and being able to access my voicemail via the web is truly great. I would even pay for this service. Unfortunately, my experiences of the past two days are getting close to the point where I don't know if I can use the service any more.
Since I started the service, there have been occasional dropped calls, annoying, but nothing too troublesome. Then yesterday, for about an hour, my phone number stopped working (similar to if you called an out of service number). It eventually cleared up, but it definitely was a big concern for me. Today, the same thing happened. This time, I went to their website, and it also was down. A few minutes later, I got the image above that mentions "scheduled maintenance". If this was scheduled maintenance, I certainly never got any notification. The only thing that is accessible right now is the GrandCentral Blog, and it hasn't been updated since October 4th. Taking the system down and not providing any notice is really unacceptable.
There are plenty of great web services that I use where I can deal with some flakiness. My phone number is not something that can be flaky, though. I would have thought that Google's purchase of GrandCentral would give them the resources to provide this reliability, but apparently all they inherited from Google was their "ignore the customer" support model.