A good, solid game worth of your time.
I didn't find a single bug in this game, something that seems to mire every new release lately. The length was perfect for the kind of game and story it was (around 8 hours) and it delivers in everything you expect for this kind of game.
I played it on the PC, and found the controls to be tight and responsive, and the battles to be fun and challenging without over-doing it. The graphics were also above par, with good character textures and decent terrain. You could say the artwork leaves something to be desired, but if you're a fan of Warhammer 40K games then you'll know why everything is brown and dark and metal in this game.
The game is basically Captain Titus (you) going from place to place killing orcs, then Chaos Marines , then both through several very alike locales. There were some memorable parts, like when you're awarded a jet pack and get to jump and crash all over the battlefield, or when you get to hold the line with Imperial Guardsmen against the Orc onslaught. You get a variety of weapons and have to switch between them and close quarter combat (with a sword, axe or hammer) to survive, and the switching between makes for a fun combat experience, especially when different types of enemy are attacking you.
If you've played any Warhammer 40K game before then the story is always the same: Humans under attack, kill some orcs, kill some Chaos guys, save the day; and here it's no different. While it's predictable, I found it really neat to experience it close to the battlefield. They try to add some ambience by locating recordings of people and their experiences, and it's a good touch.
In the end, I had a fun time with Space Marine. It was as long as it should, provided everything I looked for when playing as a giant, armored space marine and gave me some awesome combat moments. Whether you're a fan of this universe or not, give it a try, it'll make for some fun nights. However, I would wait until it goes down on price. It's a fun a game, but nothing amazing or exceptional, so I find it hard to justify the 60 bucks (Canadian) it goes for around here. Once it hits 40 or 30, don't give it a second doubt.