I bought my MacBook at the Apple Store in SF in April 2007. It has a US keyboard (obviously), which I prefer; I use my Mac on a daily basis, in the UK, and have never felt it necessary to switch keyboard formats. (Option+3 = £, and aside from the occasional euro sign, I've never needed anything else.)
Rather than buying a whole new brick and cord adapter (something like $80?), I chose to drop about $30 on a world-wide adapter kit, and just switch out the little plug nodes when I travel. So far I've used the UK one, both European ones, and the extra US one (convenient, as I left the old one at my parents' house so I don't have to remember to pack one when I go home), and I've never had a problem whatsoever.