1) The Macbook Air's trackpad + keyboard just works for me. I've tried other ultrabooks, but always end up with accidental clicks and zooms or the keyboard is a little off. The Zenbook Prime is solid and looks nice, but I don't use it as much due to the trackpad and keyboard (and this is a newer Zenbook that supposedly addressed those issues). It's nice not needing a trackball or mouse.
2) The 1440x900 resolution of the Air is fine for me. The Zenbook has 1920x1080, but I don't find that resolution very usable on a 13 inch screen. And I dislike the other cheap laptops that have 1366 x 768 or 1200 x 800.
3) I like OS X, a nice terminal, Photoshop, and a simple editor. I like being able to work on native iPhone projects. I'm not going to buy a machine with Windows 8. I run Parallels and spin up a Windows or Linux VM when needed. Very easy to slide my fingers to the right and be in Windows or Linux.