I have had similar problems. The algorithm they use is not perfect. My Nexus One used to fall back to 2G whenever my 3G got below like two bars, it was so anno

I have had similar problems. The algorithm they use is not perfect. My Nexus One used to fall back to 2G whenever my 3G got below like two bars, it was so annoying. And also there would be a temporary outage while it switched. I eventually learned how to hard disable 2G, and service improved greatly, because even one bar of 3G was better than 2G.