I'd buy HP any day...
My first experience with HP was way back in the 1980's when I purchased a HP-41c for my studies. Since then I've used many HP computers over the years from HP mini computers running UX, to laptops (I'm currently on my 3rd HP laptop). One thing I have found is most are built like the preverbal brick sh*thouse, and last for years. My HP-41c still works fine (30 years old this year), my HP TC1100 tablet also still works after over 8 years. Whilst support for the hp-41c is somewhat faded by now, the same cannot be said for the TC1100, since the HP web site still has all the drivers for the device available for download.
HP/Compaq servers have been my choice for years, partly due the support, partly due to the build quality, but in most cases it's down to the consistency of the product.... let me explain, a few years ago whilst working on a large product in one country we purchased several HP DL380 servers spread over a period of a year. Whilst on the same project here (in the UK) they went for Dell servers, again several servers all the same model purchased over a year. On the HP's we built a Linux build disk and on every server afterwards we could build the server the same from the same set of disks. On the Dell however, we have to keep changing the build because Dell had changed the parts inside every so often. Now, some would say that shows HP isn't keeping up with developments whilst Dell is. Perhaps this is a valid point, but when planning business continuity I want the same every time if I order the same model.
On the down side, HP is expensive, even if you find the exact model you want you may not be able to get it locally. My latest laptop is a HP Elitebook 8460p. The version I wanted wasn't available on the UK market. Top of the line available here (off the shelf) has a i7-2640M, 4gb ram, 320GB hard disk with a SRP of £1043 + tax. I managed to find a lower spec version for £425, then add new processor ( i7-2820QM - £225), 16gb ram (£110) and hybrid 750GB disk (£130), WWAN module (£45) - all in £935 inc. tax or some £316.60 cheaper than the one listed with a much lower spec.
That being said, I am happy to strip the machine down and change the processor etc. Many, people will not, but at least with HP the choice is there. This is now the second out of the three HP laptops where I've been able to do this because they use socketed CPU's and not surface mounted ones like many a cheaper brand, the other being a Presario which went from an Intel Core Duo 1.66Ghz (T2300) to a Core 2 Duo 2.10Ghz (T8100) with no problem. So, options like this will give the computer a longer useable lifespan than one which can't be upgraded. Finally, on the subject of support; yes, the drivers for the 8 year old TC1100 and the 4 year old Presario are available for download, however they are only for the originally supported OS not for later versions, unless the new OS comes out during the product life span, HP rarely will produce new drivers.