It's got 8Gb memory and an 128Gb SSD drive. The Intel CPU and graphics are fairly low-end; a fair bit slower than the T430, despite being two years newer, though I don't notice any speed difference in normal use. The matte 12" touchscreen is low resolution at 1366x768 but it renders colour better than my own laptop. There's a touchpad, a keyboard nipple, and the usual ports.
I installed Ubuntu 14.04, and every single thing works flawlessly. The touchscreen, the special keys and the lid camera work right out of the box, and it found our office printer without any trouble. With the lone exception of my oddball keyboard layout, I could pretty much install, restart and be on my way.
Just about all tweaks and fixes I used to do in Ubuntu are unnecessary by now. It's so polished that I really don't need to do anything. Of course I still need to install a bunch of apps and move data over; that's going to take weeks or months as I gradually find out what I need on this machine.
The keyboard is a bit cramped, and retains the dumb layout with a too-easy-to-hit print screen button to the right of the space bar. I wish they'd kept the larger Enter key too. But the feel is good and the keyboard works well overall.
The touchpad is a major regression. It's much larger than on the T430, so you easily touch it by mistake, and it lacks separate hardware buttons. Instead the touchpad surface itself buckles as you press it. But when you do, the pointer inevitably moves, and often moves right out of the area you aimed at. It seems to emulate two buttons on the bottom and only one at the top, but it's hard to tell. There's no middle button at all. You need a mouse with this machine, no question about it.
This model has a touchscreen, and it's neat. It works right out of the box in Ubuntu, and works really well. I guess this is where Canonicals work on Ubuntu Touch is paying off; it figures out when I'm moving, dragging and clicking without missing a beat. Using Inkscape is a joy, and drawing on it feels very natural. It'd be a much better input than the touchpad, in fact, if it didn't keep my hand away from the keyboard and up in the air.
I plan to separate my home and work machines from now on, but I still need to have some data available on both machines. Firefox syncs bookmarks and other things already. I've also set up Zotero to sync the biographical database through Zoteros servers, and I sync the actual PDFs through my ownCloud server at home. I still haven't decided how to handle other data, but I'll probably sync that too over ownCloud for now. A lot of it is managed by Git already, so once I update my server I'll keep it as git repositories there instead.
Overall, the big surprise is that there's no surprises. Ubuntu just works. It's now so polished that it gets out of your way, leaving you to focus on your job. The X240S is a bit better than the T430 in some ways, a bit worse in other, but overall I'm hard pressed to find any notable differences. A very non-eventful upgrade, and that's a good thing.