The MacBook Pro used to be my main work unit, however, symbiotic as OSX is with Linux it's much nicer and inherently more productive having complete compatibility with my EC2 server instances, and for that reason I've used an Ubuntu based laptop for some time now.
My latest (and greatest) is a fantastic IBM ThinkPad Edge x121e (the 11" model) running Ubuntu 12.10. The Unity desktop was something I didn't really get before but having now experienced it on decent kit I love it (perhaps even over OSX).
Unity has had a lot of grief from the long time Gnome desktoppers, and that's fair enough, change is difficult to cope with (for some), however there's no need to be afraid and to be honest (for me) Gnome seems tired and dated now with its 'programs' menu, I mean, what is it, Windows?
Up until getting the Edge I used a Dell 11z with a 1.3 ULV chip. The 11z was a great unit with excellent graphics and a crazy battery life (1366x768 + HDMI out and pushing 6+ hours use from a charge), but overall a tad underpowered with resulting restrictions for useable OS choices, which led me to run Xubuntu. I liked Xubuntu, well, up to a point. XFCE is nice and lightweight and does the job, but it just didn't feel that 'cutting edge', so when a friend offered me his i3 Thinkpad at 'mates rates' after a bif of deliberation (I already had the 11z) I went for it. Wow, what a difference, so pleased I did.
The x121e came with an i3 chip along with an SSD HD and 8GB of DDR, needless to say it's a flier and seems perfectly matched with Ubuntu 12.10. The build quality is fantastic and it feels perfectly 'right' for me on many levels. At 1.5kg it slots in the mini backpack nicely and even the battery life isn't too bad at 4 hours, more than enough for a train journey or coffee shop session.
For 'home' and w.h.y I still have the 17" MacBook, and don't get me wrong, it's a really great machine. Way too big to lug about other than between my home office and the front room, but I can't see me getting shot (yet). I use my iPod Nano daily and until Ubuntu gets iTunes (which aint gonna happen), or I sign up properly for Spotify (and get a smartphone to run it) much as I love the Edge/Ubuntu combo I still need Mac kit and OSX. Music is important to me and iTunes has achieved its goal of vendor lock-in for this media consumer (for now), unless I can think of something else.