Overall, there's not much to complain about in the gameplay departmnet. There are boss battles, but they are handled fairly well and each are very different. The level designs are fairly straight forward with a few puzzle solving type problems. Or, take control of him and make him jump into a lake or a tall building.
Or, take control of his "friend" and introduce him to some friendly fire. Or, sneak up behind him and suck out his Psi energy until his head explode. Or, you can slowly throw him into an open fire. Or, you can hold him in the air and shoot him. For example, you can pick the bad guy up and thrash him against the walls repeatedly until he dies. Having the powers affords you about serveral ways to solve any situation, and millions of ways to kill the baddies. Using your Psi powers is very intuitive and not hard. All of these things set the game apart from your standard 3rd person shooter, and make it a joy to play. You can have an outer-body experience and walk through doors to see what's beyond without getting hurt. Or, you can gain control of another character and use the bad guy to kill other bad guys. You can pick up objects or people and toss them around at will. You are given the ability to do some pretty nifty things with his brain powers.
Overall: Psi Ops would be a standard 3rd person shooter with so-so graphics and semi bland environments, if it were not for the inclusion of the Psi-Powers.