I've just noticed that when i send an iMessage to a mobile number, rather than an iCloud associated email address, the conversation is synced across my iPad and the new Messages beta app. Before this would only work if you sent the message using the 'caller id' as an email address. The problem with that was if the message failed to send due to a lack of data signal you didn't get the option to resend as an sms. I know this is hard to explain (the whole 'caller id' thing with iMessage is confusing) but hopefully you understand what I'm saying. Has anyone else noticed this?