I'm downloading it. Someone has tried this?
I run an Freenet0.5 node (Build 5109) and I assume the first FCON version connects to this still existing Freenet0.5 network. Or perhaps I'm wrong. I assume the fork of Freenet0.5 will lead to a network split (current Freenet0.5 nodes and incompatible never builds).
To answer your question: I never tried FCON and I never tried the newer Frost releases in the FCOn package.
But I keep running a Freenet0.5 node without much interaction, just for preserving this network (there's still activity, my node produces traffic, not really active Freesites, I don't know about Frost or other activities). Freenet0.5 Build 5109 runs stable for many weeks.