I am giving a try to your plugin and free service. So far it looks very good.
But I have few issues to report, which I think need an improvement, hope that will help make your plugin better.
1. A Chrome problem.
In Chrome 16, the admin page has got formatting broken -- each "block" has got the head and foot horizontal lines on the left size, and the content of a "block" shifted to the right side. It makes an impression of 2-column design with empty blocks on left and head/foot-less blocks on right.
Firefox 9 displays it OK.
2. Admin page confusion
There is no "backup jobs" concept introduced - by default it shows the only backup job. That was not clear from the beginning, as usually in any other backup application you are present with the overview, and the backup job details are displayed only on demand. Here's the concept is different. No explanation is given, but well... managed to understand it.
Minimal change, I thing, needed here is to change the default tab to Logs, with links to the configuration of the job.
3. Backup job view confusion
The "Add" button is not clear. Better read "Exclude folder". Otherwise it's like it means to add the new job...
The "Last Backup Summary" does not update with the AJAX status if came back to that page. It does show the AJAX status right after the "Backup Now" is clicked, so, it might not be a big deal to do the AJAX status check when the job detail is just opened.
Thanks a lot!