Admittedly, I'm out of the loop on iOS devices and I already have the PC version. I'm sure it's a totally valid version of that game though.
As for The Bureau, I wouldn't rule it out, but the reason I can see Enemy Unknown working is because the controls don't have to be responsive in the same way a third-person shooter does. Maybe when Logitech finally comes clean on that controller they're supposedly making...
I got it on my iPhone 5. Easily my best gaming experience on the iPhone so far. Frame rate seems solid and the controls are fine (all the problems Brad had in the quicklook are easily avoidable if you use the camera button instead of trying to move the camera with multitouch). I don't understand why the hate for the version. Sure you are playing on a small screen but that's the point. It's highly portable and offers the full XCOM experience so I can get a few turns in when I'm standing in line or on a break at work. That seems more useful to me then the iPad version. The place where I use my tablet the most is at home and if I was gonna play XCOM at home I'd play it on my PC or 360.
I also have no desire to see The Bureau come out on iPhone. XCOM works because it's a turn based strategy game so you have time to play around fine tuning your character placement before finalizing your action. I've yet to have a satisfactory experience with action games that use virtual joysticks or buttons and I don't see how they would make the game without those.
However if they announce Enemy Within to be a turn based sequel to XCOM and announce a phone version I will definitely grab that.