Yeah, EJB 3 is itself really not that new, but it took some time for implementations to come out. JBoss AS 5 took ages and EAP even longer. Then people had to upgrade from their older versions and then had to discover how much the new APIs had improved.

I don't have hard numbers, but judging from popular comments online I'm carefully guessing that it wasn't until ~2011 until people really started to see how simple EJB had become.

The old stigma still clings to it, much undeserved.