Click on the title of this post for the full lowdown. It looks like they're doing their level best to go out the classy way, without anyone holding the bag. Kudos to them for that. I feel it must be noted that I have been happy with every product of theirs I have every purchased, even if I haven't used any of them to date. Silver Age Sentinels is a fine game, and contains some truly excellent advice for running silver age supers games. BESM d20 is an odd duck, a hybrid of two systems that probably shouldn't have been done but nonetheless is chock full of potential. S. John Ross's Uresia: Grave of Heaven is one of the best small setting books I have ever seen, ranking right up their with the old World of Greyhawk boxed set. And my newest GoO purchase, Centauri Knights d20 looks like a fun place to set a sci-fi campaign, full of mystery and wonder as well as giant robots and shotguns.
Update: Not dead yet? Mark McKinnon says reports of GoO's demise are premature, but expect an announcement on the Guardians webpage later this week.