I think Dell still offer the best value for money. I recently bought and reviewed an Inspiron 5150 laptop from them (heres the review) - everything about it including build quality is great. That's not the machine for you - it's a heavy desktop replacement, and my arms ache after carrying it a short distance. More luggable than portable!

Might be worth taking a look at the Inspiron 500m though - a lightweight member of the same family at about 2.25Kg, while at the same time having good performance. If you want to go very lightweight then Dell Latitude X series (X300) is 1.32Kg looks interesting, but has a much smaller screen and lower spec processor. That's probably OK if you're mainly going to be using it plugged into a monitor and keyboard at the office (working at home I try to avoid these and move to the most suitable part of the house or garden depending on my mood!)

Before buying the dell I looked at a few other manufacturers - and although my criteria were different to yours - in my case Dell offered the best specs at the lowest prices. I was a little concerned about their support. I'd heard a few horror stories about this from other people - and about their outsourcing support to India and the such like. In the end I had a few problems with my credit card company causing my purchase to be initially declined as part of their anti-fraud policy. Dell support answered the phone quickly - and very quickly worked out what the problem was - and in fact had already sorted this out. The machine also arrived in a much shorter time than they quoted, but this is probably a policy thing!