Expandable at least. You can plug in two standard SO-DIMM chips, one m-SATA drive and one 2.5" 7mm drive. It also has 14.4" full-HD screen, big enough to use its full resolution (not retina-like ultra-high pixel density where image has to be enlarged 2x, so you get half the resolution). I'm curious about its reliability.
I'm using Asus UX-32VD which has similiar characteristics (notably it has one standard SO-DIMM slot and one standard 7mm 2.5" drive, despite its slim ultrabook-like look). Sometimes I need a bit more power and bigger screen (being "in the field", not at my desk), so standard PC does not count. I would like to see expandable 15"-16" ultrabook with 2576x1600 resolution (three columns of code plus sidebar!) and quad core processor. Ideally with one or two mSATA slots and one 2.5" bay and at least two SO-DIMM slots. Pixel density would be the same as in UX-31, so with good quality IPS display one would use every last bit of it. Something like Asus UX-51 but with better resolution and expandable. This would be terribly setup for techies, programmers in particular. Unfortunately, I'm not aware of such product - unlike desktop PCs where one can built one's own system from scratch, everyone is on vendors mercy when it comes to notebooks or ultrabooks.