I'm typing this on an X230, with 16GiB RAM. I busted the screen recently and considered an X250... it's such a shame that "ultrabook" means "one DIMM slot" these days, i.e. they max out at 8GiB RAM - same as I was using in '2009 on my old X61s!

Luckily replacement screen parts are quite affordable these days. And before anyone complains, I do use all this memory, currently dom0 has 4GB free.