The Tablet Mac (again)

So the rumours of a tablet-format Mac portable have surfaced again. I gave up expecting one a while ago (although if I ever come across a cheap Sony UX I'll definitely have a go at getting one of the OSX86 hacks running on it). The twist this time is that it may be using the iPhone branch of OS X rather than the full Mac version. I have both doubts and reservations about this. Successful as the iPhone's software keyboard seems to be (and I must admit I haven't tried it yet), I wonder how well it would cope with driving the kinds of productivity apps a larger device would need to support, as opposed to the iPhone's information-grazing "applets". With any luck, time (and Apple) will let us find out.