I didn't mind the cliffhanger, it was the rest of the season that got to me.
I'm so happy to hear JJ Abrams saying this stuff. The show just went so far downhill last season...not that there weren't good parts still.
The finale though...I liked the mask thing when it was in MI, but that's because I'm only watching it for a couple of hours and don't have to consider the implications outside of this little story. On Alias though, it's such a cop out. It's a really cheap way of putting in plot twists and leads us to never being surprised, because we will always be considering every single character as possibly being someone else. Now I hate it when shows ignore earlier points just because they don't like them anymore, but I'm gonna make an exception here. They should just stop the whole mask thing. No more masks. Pretend it never happened, make out that they're incredibly difficult to make, say they give you cancer, I don't care, just don't carry on with them.
What annoyed me even more about the finale though was Lauren revealing things to Sydney in the showdown. Now I can understand why she's doing it, she knows it'll hurt Sydney when she finds out the truth, but my god I almost gave up on the show when Lauren told Sydney the numbers with her last breath. It was so, so lame.
Another problem was Sloane. Sloane may well be the best bad guy I've ever seen on a TV show. I liked him this season for a long time, because I kept thinking "It's going to be so good when he's revealed as still being bad". The show just seemed SO much better when moments hinting at his former self returning were dropped. Like when Katya Derevko sends Jack to "kill" him, then phones Sloane and tells him to back off Irena...it was just so cool to think that Sloane was putting pressure on someone as powerful as Irena Derevko. Really made him into that intimidating figure again. I even thought he was sleeping with that therapist woman to get information off her about Sydney and Jack, but sadly it didn't pan out that way.
Luckily they might be going back towards that sort of thing, given what JJ Abrams has been hinting at. Sark being brought back to recurring (excellent), Irena probably not coming back, that Bomani guy's dead, I doubt they could hire Isabella Rosselini or Quentin Tarantino full time...the door's open for Sloane. Plus Sloane was always at his best when you saw the human side of him, with his wife. He has his daughter now to fill that role.
What else didn't I like....oh yeah, Sark and Lauren becoming heads of a Covenant cell...and then never appearing in an office and still doing all the leg work themselves. The way Sydney apparently went through a radical new procedure so she could lose her memories of her time with the Covenant, yet that completely ignores the groups she went to early on in the season full of people who went through the same thing. Am I supposed to believe they all decided to go through this procedure, especially when it happened quite a while ago for some of them?
There's so much more, but I don't feel like going through the season and picking out all the bits that annoyed me. I hope they just take the major plot points from this season, ignore the dumbass crap, and we can forget about it.
EDIT: Oh yeah, I agree with bringing back Will, if they can get him.