I'm convinced it's actually quite an ambitious game, more so than it's being given credit for. The trouble - and the possible cause of negative reactions to the demo - is that this ambition may have come at the expense of character.
It's not as similar to Dungeon Siege as some are saying. There's a lot of crossover for sure - always was going to be, given the name, but it has just as much in common with Alien Breed or Shadowrun. Unfortunately it doesn't seem bold enough to admit this, perhaps because it wants to be called an RPG and not a shooter - hence those horrible controls. It sticks doggedly and unnecessarily to Diabloesque click-to-move, but inexplicably assigns the camera rotation to WASD. Which means your left hand falls naturally into the FPS Claw, but all those years of strafing muscle memory are absolutely useless because you're actually performing an entirely different process. It seems like an insane call on GPG's part, though I'm quite sure they have their reasons.
So, WASD movement needs to be, at the very least, an option in the full game as far as I'm concerned. I do try not to be too much of a fuss-pot about this kind of thing, but I honestly did find the current control set so aggravating that I'm very unlikely to play Space Siege for pleasure (as opposed to for work) until it's patched in.
More positively - no inventory, and all the bunkum that traditionally goes with that system. Or rather there is, but it's impressively streamlined into a simple currency/upgrade system that means your mind is on the game, not the OCD loot collection/comparison. This is a Diablolike (of sorts) that doesn't want to be defined by what's probably the most ludicrous stereotype of the genre. I can't do anything but admire that - it's incredibly brave to ditch the foremost reason so many people play this type of game. Of course, this demo is barely more than a tutorial, so it's not out of the question that inventory Tetris will show up later. I do hope not.
The question is whether what you're doing instead of item-juggling - the killing of space-beasts - is rewarding enough to receive so magnified a focus. If it remains as it does in the demo, then I'm not entirely convinced it'll stay fresh. The Doom 3-like décor is humdrum, the beasts unmemorable and the combat, while fast and admirably close to actual-shooty (unlike Mass Effect or Tabula Rasa's uncomfortable faux-shooty), is horribly hampered by those bizarre controls.
I think, however, there's a lot in there that isn't entirely obvious, and a lot we haven't seen - most notably the robot companion, and the long-term effects of your choice between powerful cybernetic upgrades or hanging onto your humanity. Amusingly, you can swap out your legs for some lovely piston affairs in the demo (and there's a brilliantly silly screaming noise when you do so), but such self-mutilation has very little palpable effect, as presumably it's still beginner kit. I'm banking on the choice feeling more meaningful later in the game.
Oh - I also like the way the larger enemies' armour fragments under your fire, eventually leaving vulnerably topless scaley space-beasts. Again - there's a lot of nice little tics to it, and it's a shame that the fairly staid art style makes these tricky to spot.
So, I quite like it. I don't love it, as I had hoped to, but I most certainly don't feel like spitting acid at it. I suspect Demigod will prove to be GPG's real post-Supcom triumph, but I'm convinced Space Siege is doing just enough to experiment with its chosen form that it's worth sticking with yet.