Mad Men fans - what are the extras like on the Blu-Ray set?

A few months ago, I finished the last episode of Mad Men (all DVDs). I avoided watching the bonus materials and I plan to watch them eventually. But, if the Blu-Ray set has more material, would it be worth buying that?

It’s not like I’m going to go out and buy the BRDs tomorrow. But I’d like to buy them down the line, when I am ready to re-watch the series (especially the first 4 or 5 seasons).