The eMate is, of course, no match for the XO, though the eMate certainly has a better keyboard, and would be far better as far as that goes as a tool for writing (which is all I use mine for). I have seen an XO in real life - in fact, I have seen an SE/30 emulated on one and got to play with it briefly - and it is an amazing piece of technology overall. But the keyboard really lets it down - it'd be little better than typing on a cellphone.
Mind you, presumably you could connect an external keyboard....