The good: George, Mason, Roxy, Reggie, and Joy are definitely signed on. No word on Clancy, though. I am so glad that Reggie and Joy are staying on because I loved their storyline almost more than the reaper storyline.
The bad: Rube and Daisy are definitely not signed on, even though Mandy Patinkin mysteriously departed from
Criminal Minds and had to be written out sloppily. I am very upset, however, that Laura Harris will not appear because I freaking love her. Best of luck to her replacement Sarah Wynter, though, who at least resembles Daisy; I trust the casting people, they certainly did a good job on the show.
The new Daisy:

The original Daisy (sigh):

There's some new head guy sent to replace Rube, and he's a "slick businessman" who could "care less about souls." Also HENRY IAN CUSICK!!! is going to be in the movie, and seriously, who doesn't love Desmond to death.
I'm not even sure it's filming yet, but so far things are looking more good than bad. The screenplay was penned by John Masius, who did the main writing for the show, so you know it'll stay true. I don't know if Delores and Crystal and all the Happy Time people will be back, though.
If Bryan Fuller would've stayed with the show, I think it would've gone on longer. Sigh. Maybe the movie will make some notice how awesome it is and revive it?
Some edits:- Filming wrapped a few days ago, actually, so yes it's done. It won't be released till next year though, and it's a straight-to-DVD format.
- If the movie is received well, there is a possibility they will restart the series! There is also a possibility that Showtime will not pick it back up, and if that's the case then they will have to "shop around" for networks, but there's a new head cheese at the helm over at Showtime who happens to be a big DLM fan, so we'll see.
- Bryan Fuller, as usual, was cock-blocked from his own creation once more. No involvement here, le sigh.
- "Everyone" returned except for Rube and Daisy - I'm assuming that means we'll see Delores and the Happy Time crew, Clancy, maybe even Grandma Phil or ancillary characters like Kiffany. If we can rope Delores and Kiffany back, I'll be pleased as pie.
- Ellen says the format/concept of the show will remain the same in the movie, and she'll be narrating as usual, but there are a number of small changes due to the nature of the plot, e.g. the fact that Rube is mysteriously gone, and they are accounting for the time gap from the end of season two to the movie. Go canon!
Sources:
Wikipedia,
Muth's Myspace