I have done this mulitple times. I have never been driven to the next resort by Disney though. There was one two week stay that I moved four times!!! Every time, I handed my bags off to Bell Services and they moved my bags. Then, I went to a park for a few hours, and then took a bus to the next resort and got checked in.
I'm not sure who told the poster that Disney would move them...it isn't a common occurrence at all. Just isn't. And that's why we talk about cabs.
The issue with switching resorts is a luggage one. Yes, they will tell you that your bags will arrive at the next resort by mid-afternoon, maybe earlier. BUT...I have yet to have my bags, in my next resort, any earlier than 5:30pm!!! And that can make life miserable!!!!
From now on, I'll be taking a cab from one resort to the next. It will be worth my while to have my bags with me. If my room isn't ready yet, I can still have access to the bags!!!