Looking at the 3G coverage map for Vodafone here it has very limited coverage at the moment (and probably for quite a bit into the future also). So if you want access to the full 3G "experience" all the time, you may want to check out the coverage in your area.
I have the Sony Ericsson Vodafone branded V800 and it is quite cool.
You can switch it to 2G only if you are in an area with no coverage.
I have used the video calling in the city centre and it works well enough.
I use the 1.3mp digital camera on holidays and was able to print out the pictures with reasonable quality.
Check out ZDnet's review of this phone and of Vodafone's 3G service in the UK [broken link removed].