Just completed the demo mission - took 15 minutes or so.
Not too exciting, but not terrible either. It looks like a game that will be reasonably entertaining while it lasts, but immediately forgotten afterwards. I might just pick it up and have fun for a few hours.
Mostly because sci-fi themed games with RPG elements are quite rare and I can't get enough of that mix.
Visually, it's decent but not great looking. No anti-aliasing hurts and the engine is obviously a limited upgrade of the one they used for Dungeon Siege 2. I like the destructible environments, which did add a little something to an otherwise simplified action RPG. That said, it's not QUITE as simplified as I thought it would be, and though there seems to be only one class, there is a good amount of tweaking possible - both in terms of character upgrades and weapon upgrades. It's not the kind of game I expect to play though more than once, so it's not a typical Diablo experience. It's just a one-time thing and as such, I think there's plenty of variety in terms of developing your guy. Don't expect loot either, but rather materials to upgrade your weapons. There ARE multiple weapons that you'll find along the way, but they work like in most shooters in that you apparently get a new one every few levels or so.
The story seemed as standard as it gets, and the gameplay structure is very much like the original Dungeon Siege. There was next to no NPC interaction in the demo, and the progression seems 100% linear as far as I can see.
Anyway, not quite as bad as I thought it would be, but I think it has something to do with very low expectations. I personally love the Diablo formula, and the prospect of playing various characters for many playthroughs. But it was made clear that this game isn't about that, and so I think I was helped by knowing that going in.
In short, a mindless blast-fest with reasonable production values and enough variety in terms of developing your character to make it interesting.