I was going to PM but maybe this will help others. I totally agree with Rusty, although less from knowledge that the ASUS wouldn't hold up. I have used a Lenovo w520 since October 2011. Lightroom, Photoshop, and all the other things we do with whatever we lug around (I have a "production" desktop, too, which is like the laptop, general purpose machine.) This machine has emerged as the best -- reasonably current -- spot on the Lenovo "W" workstation continuum. The howls about the w530 and now the compromises in the w540 are a little beyond the usual "forum-as-accumulation-of-complainers" characterization. I suggest you buy a used w520.
The w520 is a Sandy Bridge configuration with user-chosen i7. get a four-core version. These chassis accept a lot of customization, like mSATA drives in a PCIe slot stashed inside -- user reachable and changeable. The optical bay can accept various after-market caddies and I now have a Hitachi 750 there with a Samsung 830 256DSSD in the "regular bay. Oh, and a mSATA that used to be my boot drive. So, three drives.
There is a configuration with a color calibrator installed in the palm rest. I didn't hear a lot of enthusiastic praise for that, but some used it successfully. (I like my Munki.) The "FD" screen is bright and a wider gamut. TN but more colorful than usual. Jury still out on the new IPS in the w540. The keyboard is excellent on the w520. There are more process light indicators on the body than is now the case. The w540 significantly changed the buttons around the trackpad.
Perhaps some time searching through this forum will help with the decision. People way more expert than I started to call the w520 the "sweet spot" when the details on the w540 emerged. Look especially at a long thread called "w540 Wish List". There are users from companies large and small that offer a VEY broad perspective on this line and its changes. "gusat", a regular, thoughtful, contributor from Switerland was part of IBM then Lenovo development (as an advisor). The search mechanism will suggest threads for whatever string you type.http://forums.lenovo.com/t5/W-Series-ThinkPad-Laptops/bd-p/W_ThinkPads
If the link doesn't show PLEASE pm me before you buy the w540.
Here's a December new w540 user's experience and related comments -- might be happy, I didn't finish the thread.http://forums.lenovo.com/t5/W-Series-ThinkPad-Laptops/Received-my-W540-today-First-impressions/m-p/1365799#M42584
I tether with this on assignments. I have brought it up to 24Gig RAM.
Important:, there is a dedicated graphics board in most w520's. There were two configurations, known as 1000 and 2000, nVidia chipset, because many of the w520 buyers were CAD/CAM people as well as photographers and designers. I bought the 1000 variant, and it's a good boost for Photoshop, and screen display tethering, etc.
There is a downside. The Lenovo-supplied and -approved power brick is just that: a brick! 170Watts (power a small town) because if you have the bigger graphics card set to run and you are rendering giant CAD/CAM environments it will stay ahead of the draw. Most of us also keep a very small 90Watter around for recharging more slowly when idle. The 90 from my previous Lenovo fit and works. Also an active and useful discussion on the forum.
I haven't been on the forum for a little while, so I urge you to go there and see what the building amount of user-evidence about the w540 is saying.
Good luck with the new machine, whatever you choose.
I have appreciated all the good advice and experience you have contributed here, by the way. And images!