Shameless Plug: I built a similar 23" Android "tablet" last year. http://martin.drashkov.com/2011/09/android-megapad-23-androi...
I thought Android is a much better choice of an OS, seeing as how many apps would already scale up nicely. I still think this is a valid product category - various specialized kiosks and smartboards will soon be replaced. I guess we'll see whether it'll be Android or Win8 (or some Apple thing).