Go with Dell XPS or Precision laptops - they are usually fully supported by Dell and are quite good hardware (USB 3.0, 16GB max RAM)

Dell has incredible compatibility with Linux - somehow a lot of Dell specific utilities have ended up in Ubuntu (e.g. firmware-addon-dell for BIOS handling, dell-recovery for creating Dells specific recover ISO, etc.)

Dell's support pages have a lot of info on advanced processes (bios flashing, etc.) from Linux - http://linux.dell.com/projects.shtml