I'll be specific for myself and then you can figure out the rest from there. I have the HTC Arrive with the Mango beta, and not just SYNC but the MyFord Touch which is a "more advanced" version of SYNC I think (it might just be an extra GUI and underlying SYNC is the same). I've seen people that say pre-Mango works fine, I think at one point in the past both the phones and SYNC needed to be updated to work together.
*For me yes it does read texts and I can dictate back.
*I do stream audio over bluetooth and for me it sounds great (10 speakers) but I'm no professed audiophile.
*I also have an 8GB USB drive that I never unplug that is filled with music (and a few wallpapers) that is always there as a music choice.
*Whatever I do on my phone reflects on the stereo and vice versa. If I hit forward/back track the stereo goes back and forth. Pause, volume, etc., all work from the phone so you can control everything from the device if you want with very minor lag (in my case though maybe size of library matters). This video might help (BT/USB works the same):
2012 Ford Focus: Bluetooth Streaming Audio - YouTube