My Eee PC has pretty well replaced my MacBook as my portable. It's smaller than what you're looking at, though there are larger models out now like the Eee PC 1000. Linux is already on them, no Windows Tax necessary if you buy a Linux preinstall. Dev tools install easily, or you can get a different distro that already has what you want, there are several that are tuned for Eee's.

A large part of the reason my Eee goes with me rather than my MacBook is that it's a lot more robust than the MacBook. I can treat the Eee pretty much the same way I would treat a book when I take it with me. It's a solid little chunk, and it cost about 1/4 what my MacBook cost.