I have put this point in a thread, but actually think it is worth discussing on its own merits. I have an app that until now runs in 2.2.1 and up. I have a few ideas that will mean that an upgrade will only run in 3.0 and up. I'm not sure how to go about informing current users of this case. I don't even know if any use this version of the OS or how many. Unless there is a way of finding out. My initial idea was to note the change in the update info when that particular updgrade goes through and it appears in the AppStore, but is this too late? I suppose I could mention it in the next update as a prompt. Any thoughts on this subject. Have you been through the same stage?