I registered my client's site with wpmu primarily for the appointments+ plugin. Graphically, the plugins are attractive. It's too bad that I have to fiddle with another optimization plugin to minify HTML... Yet that might be a theme issue.
The main reason for this ticket is that Appointments+ is not what I expected. Instead of directly manipulating a Google calendar with pre-configured figured services (which is possible), I have an independently styled calendar (that doesn't match my 'custom' colors) and a form that isn't attractive (doesn't indicate required fields either). Also, recipient emails don't include the necessary metadata to create Google Calendar events through Gmail. Secondly, there is some interesting wording regarding the synchronization of Google Calendar data (via file) and I think this should all be included in the integration - it's really easy to use the API.
I'm still interested in work on a solution and I'm sure that WPMU will be responsive to my concerns. I look forward to the replies.