I have been happy with my w520 purchased new in late 2011. These should be available at a good price used. I have not been comparing thi unit to current alternatives because I anticipate keeping it for a while. Haswell has not brought any processing speed upgrade to the table, and although the Sandy Bridge is a little less powerful than Ivy Bridge (w530) the other problems made the 530 unappealing as an upgrade at the time it came out.
The w520 is -- judging by user complaints -- better than the w530. Read though the forum for this family on the lenovo website. Read those comments. (Yes, I know a forum "collects" the users having problems and overstates the fequency... judge for yourself after reading.) Sad.
I do love the keyboard. I skipped the color calibrator. Maybe not ready for the w520 model based on comments at the tme. I like the color on the FHD (? right letters) high-res screen.
The "w" series offers a LOT of customization. I am up to 24Gig RAM. There is a PCIe slot so that got an mSATA right away for boot drive. I now have a 750 Hitachi spinning HD in the old optical bay (inexpensive third-party caddies are easy to find) and a 256 SSD in the internal HD bay. Three drives. Good unit.
Many of the users of this computer are engineering professionals. I specified the nidia KK1000 discrete graphics board. There is a "2000" variant that must be better for Photoshop. If you have more detailed questions than what is appropriate here please PM me.
Oh, and I use this for tethered shooting as well as mobile editing. Plan to keep this for a long time.
I had the w530 and thought the screen was too over saturated with colors and was not ips. I would hold out for the w540 with with high rez screens if you went that route plus the battery always had a little wiggle in it. My t430 (same generation) had the same loose battery. I recommend looking at the current line.
I've had a look at the Lenovo t430s as you suggested earlier and its review on notrebookcheck. It appears to have a display which is at leat as bad as the ASUS for gamut. Is there something I am missing here?
I still have to research the Samsung ATIV 8 you suggested.
I think I will need to find somewhere I can compare a few of these machines, but they don't seem to be stock at any of the electronics/computer stores around. Otherwise, maybe I can find an online shop with easy return policies and try them by myself...