If you're going to run ubuntu as a primary OS, the Bonobo Extreme is worth investigating from system76. I have a high-end Latitude E65* without any issues, and

If you're going to run ubuntu as a primary OS, the Bonobo Extreme is worth investigating from system76. I have a high-end Latitude E65* without any issues, and a Thinkpad W530 that is also working well - both are running CrunchBang. I didn't encounter any software/Linux-specific issues on the Dell that weren't on the Thinkpad. The Thinkpad feels nicer, but it cost a lot more. The system76 machine costs less than both (spec for spec), but I haven't used one. That said, they only build ubuntu machines - which might be right up your alley. If you want to save a little money, they have cheaper models in the 15.6" size too.