Well, I finally succeeded switching wireless carriers yesterday. I initially decided to switch carriers because my own carrier was selling new handsets to new customers at a lower price than to existing customers. Having spent some time analyzing carriers' ARPU numbers, I know that my $100+/month phone bill for the past five years is well above that of their average customer. I decided to leave.
I phoned my old carrier to ensure that my service was indeed canceled once I knew that my new service was working. I was first placed on hold for more than five minutes. Once a very distant-sounding voice finally answered, there was a "yeah, whatever"-type attitude. No questions asked about why I was switching.
I turned around and phoned my new carrier. The call was answered much more quickly by a very friendly voice who spent quite a bit of time walking me through the initialization, answering questions about services, answering questions about 3G deployments, etc.
Very different experiences.