As someone seeing it with fresh eyes, this is a pretty dismal game, with horrible immersion. The levels don't feel even vaguely real; they're just organized set pieces to make you do things in a particular order. The interface is remarkably awkward for a shooter, and they don't really explain anything, leaving you floundering.
I mean, the whole idea of the game is that you possess other creatures, and have them do your bidding, right? They DON'T EVEN TELL YOU HOW TO POSSESS CREATURES. (You have to jump into them from the back.) This is probably partially my fault for not reading the manual, and perhaps I'll get more out of it after doing that, but if you just sit down and play without finding outside help, you're likely to be extremely frustrated.
Further, the controls are really strange. It's hard to aim where you want to, it's hard to shoot, it's hard to move. Basically, in every way imaginable, it's just awkward as hell, and frustrating.
On top of THAT, your possessed character has an 'aggressive' mode and a 'non-aggressive' mode; you stay in the aggressive mode after shooting until you hit your use button. ANYONE WHO SEES YOU in attack mode (including your putative subordinates, after you take over a commander) will immediately turn hostile and start attacking. SHOOTING doesn't make them hostile, just having your gun up does. This is extremely frustrating and stupid, and it was this one decision alone that soured me on this game.
Overall, I'd say to avoid it. It's just not very good.