I have balanced the carbs on my 650 for the first time since I bought the bike, today. They were a bit off balance, and there was a noticeable improvement in both performance and the way the engine run. After the balancing the engine runs much smoother, and it performes better.
I have a Morgan Carbtune II for balancing carbs, a gift from my wife btw
, and I'm very pleased with it. It is easy to use, and the result is superb.
Here is a few pictures of the set up I used: