Yes they are, Sony also has a search site to tell you bit by bit on which games work properly and such.
Yet thanks to update patches, Sony is improving the performance of the 80GB on a daily basis.
I own the 80GB model myself and she does a solid job, just make sure to keep up to date with the newest updates.
http://www.us.playstation.com/Support/CompatibleStatus <-- that's the search site I'm referring to. Just type in the name of the game and click on "80GB"