Do not listen to the mean man. I've gotten about 4 hours in now. Mostly the SP with some MP.
Totally. Fucking. Worth it. The second I saw that Alien Commander come in and heard the music start up? Worth the price of admission alone for me. Mothership battle was fun if a bit simple. The multiplayer is...potentially good. By which I mean you have to hope that the server isn't too laggy, and some douchebag doesn't manage to hog the Devastator + Jetpack all round. There are a few good easter eggs so far, the Ego system justifies the interactivity, and there are quite a few good puzzles so far. Also, I have not heard one piece of music that I did not like yet.
Yes, the game is linear as all get out. Not that it's a bad thing at all. The Half-Life series is linear, and I can not tell you how much people suck that series' dick with praise. Duke is surprisingly quiet during "Cutscenes", and only ever says anything when everyone has gotten a word in. Alot of Duke's one liners make me laugh, and the Steroids powerup is fucking awesome. Beer is alright, but it takes a little too much away for what it gives in my opinion. The game also likes to break things up a bit with the odd driving or platforming section (which is a bad thing according to every reviewer in fucking existence). The weapons that I've gotten access to are all satisfying, aside from the Ripper. The Ripper looks ugly, sounds pathetic (Except for the reload), and has some awful firing animations. There are none. The gun just vibrates and has muzzleflash.
Also, I've encountered a turret section, and discovered that use of the actual turret is optional. Which I thank Triptych for many times over.
So far? I'd recommend it. But only for PC or PS3, though. The 360 version is a turd on a bun with a heaping helping of rotten horse radish from what I hear.