It's beyond good. ;)

No, really, I agree with most of what Fenixp said, except for the "bland" part. I didn't know the game until recently and I didn't even know about the hype, but I was positively surprised by the game. The story is meh, some characters are close to annoyingly cliché, but somehow I still love it all. I like the art style, I like the music, I like the mixture of combat action, puzzles, mini-games (racing, shufflepuck etc.), the relaxing exploration and hunting for collectables (e.g. the heroine is a photographer and you get money for shooting photos of each animal and humanoid species, even for photographing the monsters before fighting them). It's not as crazy and original as Psychonauts, but I found it equally enjoyable to play (and a bit less frustrating when worse comes to worst).

You might love it more though if you're a treehugger hippie who's into reggae and hip hop than a tough metalhead looking for something dark and twisted. (Just to join in the clichés. ;) )

Anway, it's definitely worth $5 if you can spare them.

I think it's a bit overrated as far as underrated games go.

It's got a wonderful setting/atmosphere/story/characters, the vibrant slightly alien dystopian setting where you're a photographer collecting evidence is interesting and pretty unique for the genre. But the combat/stealth sequences are rather sloppy.

It also ends really abruptly with little hope for the sequel ever coming out.

It's kind of worth playing once, but I don't think it really has much replay value.

did it a few years ago and i'd say its definitely more than worth picking up at that price

Does any of these incredibly hyped "overlooked classics" really live up to the hype? Heck, even System Shock 2, a game which I love, has reached a level of hype on these forums that it just can't live up to. Psychonauts, while fun, funny and surprisingly clever, can't live up to its hype either.

Aren't they supposedly working on a sequel right now?

http://www.rockpapershotgun.com/2012/05/08/bge2-not-yet-gone-to-the-great-beyond/

Although the popular opinion seems to be that it's looking very different from the original. Which is not necessarily a bad thing if they get the game-play right and don't completely change the protagonist.