Rated 4 out of 5 stars
I've adapted to this add-on very quickly, and it's proving invaluable. I have it set so that the "instant move" feature moves read incoming mail to an archive folder, which speeds things up nicely. It makes it very quick and easy to search for folders that are buried deep in folder trees, too.
It does have one flaw, which has been pointed out by a number of others: once the message has been filed, no message is selected, so you have to select the next message using the mouse, which interferes with the workflow. If this were fixed I'd happily move this up to five stars.