So, I've been using Google's Grand Central phone service for a week or so for real work and I think this as good a place as any to comment on the ongoing experience, especially problems. There's a Grand Central Help Group, but formal support doesn't seem to be provided.
Setting up wasn't too awful since I had recently scrubbed my contacts as part of an iPhone conversion, using Yahoo's address book as my contacts database. One reason for this was to keep my contacts from being associated with any specific PC.
Some day to day operational problems came up such as lack of support for extensions, no Skype integration (in favor of Gizmo, and no international outbound call support.
And today, when I make outbound calls using Grand Central's Click2Call feature, people complain that they don't hear anything for a couple of seconds after they pick up the phone. This has happened for 3 callers, so far, leading one to hang up.