Since installing beta 6 on my new rMBP, the Messages app rarely works for my iMessages, often saying they are "delivered" and then instead having them go through as an SMS (but still showing up in the Messages app). Friends have been telling me that they get two copies of the message, both an iMessage and an SMS. If I try to use Messages to send an SMS to someone who doesn't have an iDevice, the message just disappears into oblivion. Has anyone else run into this problem? The phone I'm using is a 5S running iOS 8 beta 5. Definitely bummed; this is the biggest feature I'm looking forward to between the two new OSes.