Over the last weekend I installed Fedora Core 5 on a Dell Latitude D810 laptop.
Unlike Jason's laptop criteria, I basically required a Dell laptop. I wanted the D610, however it was unavailable and I had to settle for the D810. Even though I customized it, I really did not have any control over what hardware specifically would be better for Linux. However one luxury I was afforded was to be able to maximize the provided features.
In fact the only features that possibly would have made a significant difference were the ATI video chipset and Wireless chipset.
On Video: My personal opinion has been the Nvidia GeForce based chipsets on laptops (I've used Sony laptops) typically outperform the ATI based chipsets. There was not much option here, however so long as the video RAM was dedicated I was satisified.
I had selected the maximum 1920 x 1200 screen and default open source Xorg driver for ATI seemed a little slow for 2-D drawing and motions. I tested the glxgears for about 150FPS (very slow), however with the very easy install of the proprietary ATI drivers, that was increased to about 900FPS (very acceptable).
On Wireless: This has always been a nightmare in the Linux world. It has improved over the past 3 years since I've used it, but too often do new hardware changes cause problems. Regardless the 2 options were an A/B/G device or B/G. I picked the B/G solution since I've seen even less success with A based chipsets. The B/G was from from Intel, which Intel does support for linux.
I was eager to try Fedora Core 5's new wireless tools (NetworkManager, etc) however I was very much disappointed. I was easily able to install the Intel ipw2200 drivers. However the default network tools did not detect my SSID and there were some problems with the connection at first. The NetworkManager caused me to lose the connection and it would not re-connect. In the end I was able to get the wireless working perfectly with a reboot.
I did have 1 minor nuisance with the Dell keyboard. The Wifi Toggle (wireless on/off button) is implemented as a Blue-Function Special Key instead of a physical separate button. As you can guess, I was not able to get that key to work when running Fedora. The syslog kept complaining. Oh well, booting into Windows fixed that. More investigation is needed as I know this should be possible to work.
I was very pleased with the Linux performance on this Dell laptop. Virtually everything worked as I expected.
The harddisk was SATA which worried me at first, but FC5 detected it properly. I even booted with an older CD with kernel 2.6.9 which gave no problems.
The pointing devices were nice also. The touchpad and pointing thumb-stick gave no difficulties.
As a linux laptop, I would highly recommend this laptop. It is a bit bulky and large but since it functions mostly as a "desktop" this isn't a serious concern. I feel I lucked out with the convenience of installing Linux on this laptop, however I hope my points help people make more educated decisions when selecting laptops.