I don't own anything Android but I do a lot of SIM swapping from my stock iPhone 4 to my jailbroken 3Gs. I love BiteSMS, SBSettings, Winterboard and the emulators. Sometimes I just need to go back.
Thinking about picking up a used Android device soon though; I do a lot of buying and selling of cell phones and I'm sure I could even make money if I decided not to keep it. Any recommendations for a good GSM Android phone that isn't super new?
Why not jailbreak your iphone 4?