I also don't see how this screws MS. I'm sure if MS really wanted to bundle GTA4 with an Xbox then it would happen, of course with a deal having to be made which is the normal business way. It's pretty obvious I think that in most countries the game will probably ship more copies for the 360 than the PS3 overall for the initial release. You really just have to check out the top pre-orders from different suppliers to see that. At the moment both my local Game and Gamestation have told me it looks like they will be selling more copies of the game for the Xbox than the PS3 at launch. But, I'm sure this bundle will help the PS3 in the long run, and this is only a good thing after the slow start by Sony.
I do own both consoles
I will be buying the Xbox version at launch