For the past 10 + years, I have been using Linux exclusively as my desktop environment, and all on laptops. I use Kubuntu 14.04 at present, and have been on the LTS versions for many years.
I only buy laptops that are on sale, whatever is in the flyers the week I need to replace a laptop.
From a 'what works' point of view, most of the laptops I have used have fully worked with Linux. That includes Wifi and sound, the most pesky components. Years ago, one Dell laptop had an issue with Wifi and I had to download something or other to make it work. The last few releases did not need anything special for it to work.
I am writing this from a 2009 Toshiba that works well with Kubuntu 14.04. An older Toshiba (maybe 2006 or 2007) still works fine with the same Kubuntu version.
From a reliability point of view, avoid HP laptops. I had one where the screen hinge decided not to work, and broke, so it is now a special purpose server. Another HP was overheating and we got it exchanged under extended warranty and 3 strikes (sent for repair 3 times for the same issue).