My biggest complaints with the XPS 13 are the screen (terrible viewing angles) which won't be the same in this developer edition, and the trackpad, which has abysmal palm rejection and multi-touch gestures.
In a never-ending quest to find the MacBook Air equivalent for users who refuse to use a Mac, the X1 Carbon is the closest I've found.
* 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
I've owned a number of thinkpads (t41p,t61p,x220) and all have been depo repaired under warranty at one time or another. Turn around has NEVER exceeded 4 business days from time of calling the support center. Replacements include the logic board, screen, or just them sending me a replacement hard drive.
As always, YMMV.
The glare of the gorilla glass in the XPS is my concern, and overall screen size is also larger in the X1. IPS vs the TN panel... I really just want to see them side by side.