3G is a rubbish network, don't worry about them.
The Sony Ericsson's are great phones. I still have my w800i that I got when they first came out and still really like it, the walkman range are excellent if you plan on using it as an mp3 player as well as a phone. I'll definately be upgrading mine to a w900 or something at Christmas, or whichever is the best SE at the time.
They are definately recommended from me, I really like them
edit: oh and as for you concerns over the size, they really aren't that big - they aren't tiny but they aren't too big either. Good phones all round