I do not have any Nonatron 300 units now. But, I have in the past. I liked using them. They are easy to set up and use.
They are nice lights and the modeling lights do track with reasonable accuracy. I suspect as accurately as the competition (but I never did any side by side tests).
I think the method to attach light modifiers is adequate, but not as good as some other lighting systems.
If you can get a good deal on the M300 units get them. They are good lights.
But, if I were buying new today I would choose the Alien Bee gear over the Novatron.
The Novatron units are fine, but you get a bit more value with the Alien Bee units.
The AB800 has about the same power output as the Novatron 300.
Enjoy! Lon