Ultimately, TimeShift's most significant flaw is in going soft, not forcing the player to make better, more creative use of the time manipulation feature. You can, more or less, blast your way through in stock shooter style; most players will assuredly choose this path of least resistance. You can do some amazing or hilarious things, oftentimes both, with your time-shifting powers, but you are never required to do any greater analytical thinking than that required of the usual puzzle-solving in standard shooters.
Time-shifting or no, it plays like a traditional, exciting, sometimes intense FPS, but it's been released in the face of several exceptional examples of FPS titles. Six months from now, during the midst of the annual games drought in new titles, shooter games no better than TimeShift will be favored by some, if not many, critics and will also sell well to a thirsty FPS audience. To significantly mark off this title right now would be, if you'll pardon the pun, merely a matter of timing.