I am. I get a much better signal from 3 than O2 (North/South Yorkshire) but I can't really compare much to Vodaphone. One of my lectures was underground the other day and I got a signal when my friend on Vodaphone couldn't, though that could be a one-off location specific thing. Customer service isn't amazing (couldn't really understand much) but I've only used them to switch my number across. Everything seems to be fine tbh, not once have I thought about switching. Also amazingly cheap (32GB iPhone 3GS on sale earlier this year) but obviously it's irrelevant in your case. Hope that helps somewhat, don't really know what else to say.
