I wonder if I'll be able to send texts to people that don't have an iOS device on my iPad? It's annoying having to reach for the iPhone to reply to text messages
Doesn't look that way from what information is available. The moment I saw the bit about iMessage I was thinking "please let this thing take incoming SMS messages on my iPhone, sync them to all of my iDevices via iMessage, then send an SMS throgh my iPhone even if I write the actual reply on my iPad through iMessage".
That would have been a great feature.
On another topic, Photo Stream seems like a nice way of giving someone a near-live glimpse into whatever it is you're doing elsewhere. Take photos on your holiday and assuming you have 3G connectivity, your folks at home will see your photos nearly instantly through an iPad for instance (assuming both devices use the same Apple ID). Neat.