Shucks. I forgot that last suggestion.
I just picked up a Go Phone, and the wife is using my previous phone, which I hated. The Go Phone is just slightly different enough that I might not hate it, but we now have three batteries and three chargers to share between the two phones.
And believe it or not, the guy at the ATT store actually told me about the switching-sim-cards-with-GoPhones thing. Just said they couldn't sell me one for that purpose.