The realities of bringing any handset to market are almost unimaginally complex - spectrum approval, carrier acceptance, interoperability soak tests etc. And thats before marketing, distribution pricing! With a new OS only someone with Googles backing could have done it. Basically they have paved theway by eating their own dogfood, and the torrent of other handsets will begin in earnest next year.
I'm looking forward to seeing all the form factor permutations. Think of things like a pure candybar Android handset with just a numeric keypad, or a super slim one, or a flip model like the RAZR, or even a super cheap one with no frills so they can be given away with cornflakes (or at least sold by the truckload in supermarket aisles!).