Well, not much...
1. If you flip the stimpmeter over, there is a notch have way up the meter so you only have to roll the ball half the distance which is useful on greens with excess slope. So if a green "stimps" 6, multiply by 2 and you have a 12.
2. It has measurement marks on the side so you don't have to carry a tape measure with you. At HCC, I used a permanent marker to do the same.
3. It's blue...not green and has a nice USGA logo printed on the top. The old stimpmeter has USGA stamped on the under side.
My guess is the USGA needed to raise some money and or are concerned with competition of the Pelzmeter, which is a far more accurate way of measuring green speed.
After all, it is simply a piece of aluminum with a notch in it.