Pandora's looking cool, but I don't game enough to afford it.
Kindle is nifty, maybe the next-gen will get me, but it'd better beat the N900 in DPI and total pixel count, or I'm out. (OK, maybe if it had BT so I could use it as a modem I'd get both )

Cloudbook developer's version, or one of the other badgings of that hardware, is probably it.

Unless someone comes out with a head-less laptop-server sometime before I buy it... Think of it, modern laptop computing power, without the diagonal size accompanying a laptop. Keep it in your backpack and VNC with the N900, or use it (with full-size keyboard and touchpad) on your lap with the N900 sitting on top, in front of the keyboard. But noone will make such a thing, I'm sure.

Edit: Looks like Karel beat me to mentioning Pandora, but I still can't justify a dedicated gaming device.