I can't speak to your exact question, my two sites are connected by multiple 10Gbe fiber links I had laid between the buildings.
I am using Comcast Metro Ethernet for my primary internet connection though. I originally signed up a few months back for 20/20 as a test to see if it would be capable of replacing my DS3 as our primary connection. I didn't tell anyone I was redirecting web traffic but within 3 or 4 days people actually said "the internet seemed faster". I've actually been happy enough that my circuit is scheduled to be upgraded to 100/100 on Tuesday and I've asked my account rep to come out to discuss voice PRIs to see if I can drop Verizon.--