OK, so inline compression on non flash systems does have an overhead to be aware of, but depends very much on your system, if your controllers are already running with high utilisation then inline compression can have a serious impact...
you can inline compress on non flash systems, but just be wary of the overheads.
inline compression is on by default on AFF systems.
you can post compress, on non flash, so that will give you potential benefits without high performance impact, no massive penalty that i'm aware of with using compressed data when you are reading it back.
as for benefits, depends on the data of course, if it is possible to compress it, then you will see benefit, i've seen plenty of sites where there is significant advantage and capacity savings to be had with compression, way over those seen wth dedupe.
but as with all compression algorithms it depends on the data and how well that it can be compressed.
so is there benefit? possibly, it depends.
can you run it on non AFF - absolutely but be aware of potential performance overhead.
hope that helps.