* Trackpoint!
* Keyboard feel. Even the chiclet ThinkPad keypads still have "IT" for me.
* No more fn-key chording needed for Home, End, Delete, Page Up, Page Down.
Plus a non-technical, possibly silly, reason of "it's not what everyone else and their mum has." I also like the looks more (black is the new black!), though on that I realize I'm in a minority (I did love the rounded original MBAs, however).
On the other hand, my MBP's screen has much better colors than the T430s's. :(
And yes, no proper laptop should ever be sold without a trackpoint and a proper keyboard! :)
Having both a standalone, "classic" Thinkpad keyboard and a Thinkpad with the chiclet keyboard, I find the resistance on the chiclet much more satisfying. Best keyboard I have used so far.
EDIT: For clarification on power consumption, the best idle draw I've seen anyone get in my moderately extensive research into running Linux on this machine is 7W; under OSX, it's fairly easy to get down to 4W.
But Windows is a terrible environment for developing almost anything other than Windows-only stuff like .NET and PowerShell