Greg's focus is clearly MS-centric, as he claims not seeing someone's Exchange calendar on an iPad is a deficiency of that device. Only if you care about Exchange. Cloud adoption, by definition, ends vendor lock-n. If Exchange's proprietary calendar interface won't work with HTML 5, who is to blame? As my da used to say, it's a poor carpenter who blames his tools for crappy 'implementation' (last word is my version, sorry).
Greg makes his point clear: "Software providers will be given a tablet platform in which their full-featured applications will work out of the box. In order to tailor the app for Windows 8 tablets, there will be GUI changes to make the tactile experience easier – but the app does not need to be re-written." Don't re-write to leverage the platform, but stick with your old, hackney code.
No, thanks. Objective C development on the iPad and iPhone has yielded amazing new apps, not possible in the previous MS-centric world. Building true service-oriented enterprise solutions opens the door to platform flexibility. Few would argue that the iOS interface is the benchmark for touch on a mobile device; slapping some oversized icons on Windows is not a solution. Re-thinking your approach to integration of enterprise, mobile user needs, and freedom of data is a way forward... IMHO.