sbiddle: The XT Samsung will only give limited 3G coverage on Vodafone since it doesn't support the 900MHz 3G frequency that Vodafone use outside all Cities.
As I said above I haven't had any problems with a 850/2100 used on Voda/2D on 3G. What i have found is that if there is no 3G on 2100 then there's a 99% chance of no GSM as well..