One last minor problem...
You have to strain your brain now to come up with a software nitpick, but the frame structure that allows fast reloads also means that the bookmarking of messages is more difficult. You have to add the site to your favorites list, then go in and get the actual URL of the message and edit it manually into the favorites listing.
I don't archive messages often enough to make this any kind of real problem, but if there is a quickie workaround that would not sabotage the more important fast reload feature?