OK well i haven't played any of the online yet so i won't be able to say anything about that. But the campaign so far is pretty good, i don't know how close i am to finishing, but i'm about 4 hours into it.
One thing i like about reach is the updated forge. I can't wait to see what people create, since most were able to make pretty amazing maps in halo 3.
(FPoS, GPoS etc Evan, lol)
One thing i don't like about reach is that you can't fly pelicans =/ i really wanted to try it, whether it would make sense or not in campaign or an online game, but falcons are pretty cool too.