I've seen some pretty cheap stuff already (WinBook 7", $70, 1GB RAM, Windows...) so my figuring is that the Win can't be worse than that (which was actually pretty okay).
The last time I ran emulators on handhelds were a Dingoo A320 (RIP battery) and some PSPs, so it'll definitely outperform those. Not sure about native games, I know plenty will run but haven't particularly looked into it.
Granted, I'd say most of the want for this is the cool factor (Clamshell Windows? Old tags like UMPC being relevant? Sign me up!) but I'm sure I can come up with something to do on it, even if it's just Steam In-Home Streaming.
(Steam streaming, strangely, works far better for me than any attempts at Moonlight, so there's that.)