I primarily use gnu/linux and I'm planning to upgrade my laptop. Any recommendation? rMBP, Zenbook, Carbon X1...? Long battery life and performance are the primary criteria.
I have a lenovo x230 that works great for me... It's not as high-res as an X1, but it is super easy to swap in 16G of ram and an SSD. I think the X1's ram is soldered. I also have an extra battery that snaps onto the bottom which will give me ~10-12hrs of total battery life when I'm going about my usual business.
If battery is your primary concern you should hold out for Haswell.
I have ASUS UX31A (Core i5 version). Pretty happy with it. Get 6-7 hours with WiFi on.