The ones I found were: Asus Zenbook, Samsung Ativ, Lenovo Ideapad (2-in-1)
The Ativs are really nice except for the "Windows 8 COA BIOS key in system, need to download copy of Windows 8 from Samsung" that was one ebay listing I saw.
The Carbon X1 is a good series but has fan, also battery life not good and 14"
I'm favoriting your question as I'm looking myself. It's tough man, a lot of the older computers don't have good battery life or are stuck with 4GB ram. Macbook Air 2013 is probably your best bet as far as actual battery life/build quality but it runs Apple OS, you could dual-triple boot that was an option I was considering myself however the battery life is partially software on Apple's side.
The Dell 13.3 edge displays are nice haha, surface book would be nice as well, but yeah out of budget.
There are some other ones that slip my mind. So many times I was sold on a laptop then found problems like heat/battery life/display problems.
Right now I get away with 13.3" (Samsung Chromebook 2 Exynos $140 (slow processor)) and Cloudbook 14 by Acer (battery life $99 good battery life longer in Windows than Linux with TLP I tested 9+ hrs), but these suck 4GB ram, 2GB ram respectively. The chromebook what's nice about it is the screen/size. I have crouton on the chromebook but it's not as convenient as just having full linux (watching shows better on chromebook side).
I'm mostly productive on my 8GB desktop though with 2 screens. Laying back coding in bed has yet to be proven productive for me haha but that's the "reason" I'm trying to find a good dev ultrabook for cheap. I'm also concerned about theft, so the idea of lugging around a Dell 13.3" edge display xps... I don't know what I would do if someone just stole that... so a "disposable" but useful laptop is appealing. This Acer Cloudbook 14 is close but that fixed 2GB ram damn...
Keep in mind my search is for ultrabook, hopefully the fans either don't exist or are positioned in a way where you can set your laptop on your lap.