My experience...
I experienced lag in many games while using VM's 20Mb service (it was far better on their 10Mb service) and now I have a 1Mbit service (crap due to the distance my new house is from the exchange) from Andrews and Arnold I have very little, if any, lag while playing the same games (CoD, Battlefield Bad Company 2, Forza 3).
I reported it several times to their tech support and all they did was send out a man to replace the cable modem, which solved nothing.