The limitations vs PC is the controller. UI's in games that are designed for both are dumbed down so much that in-game controls are focused for the controller which has a limited number of buttons vs a keyboard. It becomes obvious that game design has been so simplified you might as well wear a stupid hat.
I'd say it's still price point, controls, and long gen cycles. In the past the long gen cycles caused development stagnation, but we've yet to see if MS will keep their word on the claimed new shorter cycles. A lot will depend on how well One X sells and is supported by developers.
Also, dev support now means more than just them committing to a high priced (for consoles anyway), smaller niche product, it's also a guess as to how many will actually offer the proper KB/M support MS claims to want to genuinely offer.
Though MS are concerned ( as they should be) about KB/M support being done properly, they are going to leave whether it's done and how it's done up to the devs. This could mean the only games you'll see with proper KB/M support might be just the ones MS publishes.
The how it's done they want to mean being given proper, separate control scheme designed specifically for KBs and Mice, but they also prefer multiplayer servers give players the option to play only with those of like controller types.
Just the fact that the latter has been the Achilles Heel in attempting to blur the lines between console and PC for decades, kinda puts it in perspective, and is a big part of why many are skeptical about whether it's really going to happen.
When you think of people playing on consoles, but limited to PC servers if they use KB/M, it's almost pretentious to think of it as actual console gaming. It's kinda like when you were a kid. You were invited to eat the holiday dinners with the rest of the family, but you had to sit at the folding card table with your little nephews, nieces, etc. It doesn't tend to make you feel like part of the family. Except here, it's in reverse. OK, so you found a cheaper system, but if you're going to play with those big boy controls, you better sit at the big table too.
It gets even stranger feeling for PC players just looking to play the console exclusives they can't on PC. At some point MS is going to have to decide whether they really want to bring all their console games to PC, or whether they want to get real and stop BSing us, because lately they're tip toeing a line in between the two that has an unclear outcome.
