So far I have had 5 to 6 laptops on which I have had linux installed.
1. Acer aspire - some old model during 2006 year days, graphics card from SIS, had lots and lots of trouble in getting things working with ubuntu. Early days of ubuntu I think might be responsible. But from that time I decided I would never buy a product which has SIS. No support for linux.
2. Dell Inspiron - ATI graphics, in 2007 early months, had some problems with ATI as support for linux was nascent in those days. ATI support for latest graphics card for linux is crapy so if you are planning to buy a newer laptop with ATI then good luck with linux.
3. Lenovo T61 - good support, again ATI support was not good, with 3d acceleration etc it was not comparable to current laptop. But overall pretty decent, things worked out of the box.
4. Toshiba Protege M500 - Pretty old laptop, so no problem in getting linux work. Only problem being with mic for skype and audio muted if muted in windows and if logged in to linux. Jaunty or may be Heron fixed the issue. Still use it as it is my company laptop ;-).
5. Asus M51Ta- Night mare... no fault of asus though, ATI again, dual graphics card, it sucked big time in support. Would have preferred one single card instead of two.
6. Dell Studio XPS - boy does it work, every I mean everything, webcam, wireless, graphics card (Dual), bluetooth, mic, hdmi, even audio through hdmi... everything works right out of the box, drivers for nvidia installed but for graphics and drivers for broadcom wireless .... and it is like a breeze... has slight heating issues, would be doing copper mod shortly to reduce the heat, waiting for copper, thermal compound to be delivered... next upgrade on it would be an SSD drive.... but would wait for another 6 months for prices to go down....
Studio XPS M1330 highly recommended if you want every thing... I mean EVERYTHING to work out of the box on your computer using linux....
GO NVIDIA... ATI ... learn something from them...