^ Laptops are more susceptible to slowing down because the hard drives are slower than on desktop machines running faster-spinning 3.5" drives.
Dell laptops - I've set up dozens of them in the last 6 - 12 months and haven't had to phone customer service once because they've all worked flawlessly. They are great build quality, especially the Inspirons at the lower price range (don't like the 1300 though but what do you expect for £200). I own a Precision M65 which is just excellent and I couldn't fault the build quality in any way - brushed aluminium finish, weighs a ton, feels solid, runs very quiet. Had an Inspiron 510m for 2 years before that and it's still going strong. (Current user has it running 24/7 doing various bits & pieces)
"Don't trust their batteries" - batteries are batteries, nobody makes better or worse ones really (apart from cheap non-branded ones) - and besides they're all made by the same manufacturers that apple and hp etc. use. One of the 4 batteries I had for the Inspiron 510m was faulty, I phoned Dell, they posted me out another free one - the faulty one then started working a week later so I got a free battery