DownThemAll! is not going to port to the new Firefox add-on framework because he doesn't think it's possible with the new locked-down API. However, he did decide to do a DTA Lite.
There's only one plugin I'll miss, which is the one I used to pull videos off of Nico Douga for stuff like the Japanese pony episodes, but I can work around that. However, I also don't have any particular urge or need to use Firefox for anything except sites that need a heavy dose of NoScript. I really don't think they thought their schedule through for a move this huge.