My first machine was the Sony AW series. I ruled the machine out because of the unacceptable size and Sony's policy of refusing parts necessary to perform system upgrades. The LCD looked good but I didn't test it.
I ruled out the Lenovo because it has the narrowest gamut and used CCFL. That may have been a poor choice but that's what I thought at the time. I also ruled out Dell's M6400 because of its massive power supply and mandatory $1000 graphics option. I tried to obtain an HP DreamColor notebook but HP direct turned out to be too difficult to work with. I ended up purchasing a Dell M4400 15.4" notebook.
Installing OS X is doable on a Dell notebook but supporting the various peripherals is a lot of work and power management isn't great. I made the machine work well enough to test and benchmark but left a number of components unsupported. Having a quad-core processor made the Dell more than a match for any Apple portable running photo software.
Shortly after my Dell purchase, Apple announced the new MBP 17s with a wider gamut so my efforts shifted toward comparing the two. Here's the result:

The first graph shows the new MBP display against the old CCFL MBP 17. AdobeRGB is shown in white. The new display has a much broader gamut than the old one.
The second graph shows the new MBP display in green, the Dell M4400 display in red, and my NEC3090 in blue. As you can see, the Dell has a larger gamut overall than the Apple but not in all areas. It's not clear which display is better for UW shots between the two. Because of that, I have cancelled my pursuit of OS X on the Dell and will be keeping the new MBP. The Dell is much faster and has some nice flexibility features (like dual hard drive) but it's not enough to put up with the downside of OSx86 for me. Leaving "the fold" is only justifiable to me if the advantage is compelling. The Dell doesn't accomplish that but it would make a great choice for Windows users.
Both notebook displays are 6 bit and posterization can be seen on test images. On real images I haven't seen a problem.