Given what's going on with HP and the PC division, I'm not sure buying an HP at this time is a wise idea. For Dell, just hope you never need customer/tech support or warranty service.
The Lenovo W520 might be worth a look. It's touted as being geared toward graphic work. Don't know what type of display panel it has but don't believe it's IPS. It can be configured with a built in colour calibrator. Not inexpensive though.
Either way, I still wouldn't use a laptop for truly critical work. I've got an Acer Travelmate at the moment and I'm surprised at how good it is. I can get reasonably good results with it and for a 'quick and dirty' it's quite good but still come back to the shop for the heavy lifting.