I noticed that when I get a text message and I'm already in the messaging app, the notification tone is different from the one I get when I'm not in the app (the one I chose in the settings). I'm guessing this is just a quirk that no one picked up on in testing? Just seems slightly odd!
Also, it appears toast notifications are missing for new emails. This again seems a bit odd. You can set the phone to make a sound when a new email arrives, but if you're in any app at the time you've no idea what that noise is for? Another oversight that will hopefully be fixed in a software update?