at some of the posts. No, Federer does not have a great ROS compared to the other top players (look at the stats). Yes, Federer's return used to be great. Not in aggressiveness, but he was unequaled at getting returns in play. This is one facet of his game that has dropped a lot in the past 2 years and that I don't think he's ever going to get it back.
This pretty much sums it up.
Fed's FH return is still quite good. His BH return has always been pretty defensive. Previously, his speed (and thus defense) and ability to take control with just one FH were enough to put immediate pressure on servers. If he got it in and pushed it deep, chances were he'd win the point.
He still plays it defensively, but now he lacks the speed and FH to consistently take immediate control. Plus he misses the block-backs a lot more than he used to, probably a slowing reaction-time thing or an attempt to keep returns low and thus from floating and then getting crushed past his deteriorating speed.