We did it. We bought a 20gig colour one.
We thought for a while about getting 2 minis and just swapping them around, but we ended up with the 20gig because even 2 minis don't hold nearly as many songs. J's been loading it up while I've been at work so hopefully I'll be able to play with it a bit in the next couple of days.
It's far heavier than I expected, but I do love it so.
Let's see, we got it in the US, and I can definitely back up the "no need to buy the special adaptor kit" thing - just plug it in with a plug converter and it's fine. And I can also confirm that the cost savings of buying it in the US is negligable. I think we probably only saved around £20 but we had the cash and it seemed stupid to convert it back to pounds 'cause the exchange rate wasn't all that hot. If you can get a good deal in a duty free shop you might do better - I know there's a Dixons at Heathrow. We got ours at Target which was pretty much the cheapest place, but their stock was pretty low and we had to go to two stores to find the one we wanted and even then we got the last one.