Another nice-looking alternative
So I realize this thread has been going on for a couple years now, but I also ran into this problem. I didn't rush in buying the Moen extension plate. I instead went over to the local Home Depot and just started walking around looking for anything that I could mount on the front or back of the mounting plate and with a matching Satin Nickel finish.
In the faucet repair isle I found a satin nickel lavatory mounting ring (http://184.108.40.206/details.asp?ProdID=85) that worked quite nicely. Using some adhesive caulk, I glued the included rubber washer to the mounting ring and then the ring to the mounting plate.
The end result looks better than what I would have achieved with a correct install.