Game duration has increased since MM started taking games played into account.

http://i.imgur.com/iymSe6N.png

Blizzard officially confirmed the changes on the 16th but the data shows that the change went into effect at least a week earlier than that. In the week of 7/5-7/12, there was a universal spike in the length of games, ranging anywhere from 14 seconds to 49 seconds, depending on the map. There were also a few reddit posts from over a week ago when people noticed their queue times increasing. I'm guessing the change went into effect mid-week as well as the game duration continued to increase the following week.

The reason I decided to check the data is because I personally felt like most of my games were closer and taking longer, and the data seems to have confirmed my suspicions that overall game length has gone up since the change.