"Ordinarily, the release of a single ultraportable Mac should not be reason for Redmond to quake in its boots, but yesterday's announcements by Apple should give the Windows team plenty of reason to fear. It's not that the product itself will put that much of a further dent in Microsoft's still-massive share of the PC market. However, the product demonstrates some capabilities that the Mac now can offer that Microsoft would seem to have a tough time matching."
My guess is, no, they're probably a bit sorry that they didn't push harder (and sooner) on the SSD concept, but their market share remains overwhelming, so worry, probably not. The gauntlet has been thrown down. There -are- Windows-based laptops that match-up well with the new MacBook Air, when hardware is compared (the Sony Vaio X is mentioned). But, Mac OS X really gets a boost when run on an SSD. The instant-on (from sleep mode) really is instant. When I'm done with Windows, close the lid. Ditto for the Mac. Open the lid, both come back, the Mac almost immediately, Windows needs a bit more time to awaken.
As for building more 'iPad-like' features into the Mac, it's a good idea as long as the 'old ways' continue to work. Windows has had touch capabilities going way back as well, so as operating systems evolve, we can expect the distinctions to blur a bit. Witness BootCamp and virtualization. Admittedly one-way to this point, but maybe the Hackintosh community will succeed (and/or be commercialized).
The concept of an App Store for the Mac is intriguing. Anyone who has ever searched for software for the Mac or Windows (or Linux) knows how iffy the whole process can be. Bad code, Viruses, Spyware, Keystroke Loggers, ad nauseam, are rampant. A "trusted" source is really the Holy Grail of software, so of course Microsoft will follow. Again, who benefits besides Apple and Microsoft? All of us.