Well, i didn't appreciate all the times there was no sneaky option, but rather you _had_ to kill a lot of guys in open gunfight. But then again, that definitely added to the difficulty of the game. And I guess you were still kind of sneaky even during those fights (and MAN was the AI stupid).
I didn't have a problem with the game being short, still worth the investment I think. Especially if I can play the coop.
I did have a problem with the very linear sort of sneakyness (oh look a pipe in the ceiling).
It's way more simplistic than the game before the last (never played double agent). Far less pathways, more brute force (on the last levels it often felt like it was more about tossing grenades around than sneaking) etc.
The lack of a save function makes the game even more platform-like, but in this case it's something I like, because apart from a few places it just upped the difficulty, rather than made a chore out of the game, if you see what I mean.
For me I guess the lack of a sneaky option made me broaden my views, as I generally tend to prefer that option than the barge-through-the-door variety. This can be fun, too.
all in all, I'd recommend it if you're not strapped for cash. It's a couple of hours of fun gameplay, with a few new really good design implementations. But it's not omg-get-this-game good.
(also, please get it so I have someone to play the way more sneaky coop campaign with)