I'd look at the GiiNii Mini Movit (Android non-phone device). Unless you want the WWAN, in which case: look at the G1 if you want a keyboard, or wait for the imminent G2 (supposedly based on the HTC Sapphire 2.0) if you don't. (unfortunately, there isn't a "data only plan" for the G1, so you can't ONLY use it as a data device)

It's not going to be the best PMP, but then, I don't think of the NITs when I think of media players, so everyone who gets all up in arms about media capabilities just sounds silly to me (if you want a PMP, get something like an Archos, not a new NIT).

It's not going to be the best game machine. If you want that, look at OpenPandora or a PSP.

Android is, however, a good, solid, generalist platform that happens to be open source. You don't get an xterm for accessing it's linux layer, but there are things like SSH and VNC clients for it, so you can access the shell of some other linux/unix box if you want. And there's already a fairly nice application ecosystem for Android.