sound is ok for a $140 deck. I wouldn't say it is a LOT better than stock, but given its additional capabilities I'd say it is worth it.
WMA, MP3, AUX In, iPod and iPhone compatibility which can be controlled from the deck.
The interface is a bit clunky in that it is not super obvious on how to change settings etc. Usually for me, I can spend 5-10 seconds with a device and figure out its interface, but with this I actually had to reference the manual. When I first got it in as well, FM wasn't present. I had to reset the deck in order for the tuner to come in. I haven't had a chance to fully listen to the output of this deck, but I'd say it is better, but not significantly better than stock.
One thing to note is that when the iPhone is connected, it can only be controlled from the deck. Another big WIN was that the USB port on the front of the deck charges my iPhone which is clutch so now I don't have to replace the car charger that my wife stole. =)
Here is a pic of the iPhone when connected via usb to the deck.