I'm going to be switching back aand forth on one SIM card depending on my mood. If you have both and do this via one SIM card, is it a pain in the *** or relatively smooth? The one thing I worry about is iMessage to SMS and back. Will I need to deregister imessage each time? I'll likely be switching weeks at a time. Any thoughts or experiences with going from OS to OS and back would be helpful. Thanks.