I checked this three days ago after reading the Mozilla blig post, and literally none of the extensions I wanted (except the ones already available on stable) were available. The list of available extensions, even on nightly, is very small.
Perhaps it will grow but I'll wait to see that before I believe it.
I'm still waiting very basic and popular extensions (uMatrix anyone?) for SEVERAL MONTHS.
And try to offer community help. Ha!
mozilla have to die for firefox to live.
uMatrix and uBlock share the same base code, and we have uBlock but no uMatrix... it is all so rotten. Almost like mozilla is actively breaking firefox.
Perhaps it will grow but I'll wait to see that before I believe it.