Thanks to all of these posts here, this is how I solved the poor WiFi reception problem on my newly purchased brand new 2.4Ghz Macbook.
It exhibited the following symptoms: terrible reception, which I define as two reception bars, when less than a foot away from the Wireless access point!
Reception was poor at work and at home. As a point of comparison, my old G3 iBook got full reception at work and home.
I returned my brand new Macboook within a week of purchase, via an Apple agreed DOA (Dead on Arrival) number. Macwarehouse then very kindly provided me with a new replacement Macbook. No fuss, no arguments, no hassle.
If your Mac is new, don't waste time. Return it for a full refund or replacement. I refused to accept a tediously lengthy repair process when I'd be without a computer for up to three weeks. Under the UK +Sale of Goods Act+ you have a strong case. I only had to mention "The Sale of Goods Act' 1979 and subsequent amendments", only once 🙂
http://www.berr.gov.uk/whatwedo/consumers/fact-sheets/page38311.html
For those of you with warranty-expired Macs with this infuriating problem, there's a five year window for claims.
Let's hope the replacement Macbook's not got the same hardware problem.
p.s. I only wish that I could run the 2.4Ghz Macbook on OS 10.4