I have been using former eyeon digital fusion on and off since version 2, long long time back.
Since Blackmagic took over the software they ported it to MAC and thankfully did not let it die.
On the contrary! They develop fusion in a nice way and the update to 9 is something you do not want to miss.
Just go to their site and click the "Compare" menu button. You can see free fusion and studio side by side and
decide for yourself what of the studio features you really need/want.
The free version is more then capable of anything you might want to achieve, I`d say.
It is a direct competitor to Nuke. I like it better, but that is just because I am used to it, I guess.
You can do more or less everything in one way or another in both programs.
Can`t beat free
And the price drop is crazy. It is worth much much more.
Cheers, Klaus