Medialas published the new features when they introduced Mamba 2.0 and MIII, but one of the bigger ones was the 3D rendering engine. With 2.0, they also fixed a lot of irritating bugs like resizing effects on the timeline which caused them to disappear / overlap or have tiny time gaps with the effect in front of it. Before 2.0, Mamba Black had memory leaks and a myriad of issues that caused BSDs. Assuming you need backward compatibility with Mamba Black, I think 300 Euros was well worth it.
Your other option would have been to export your shows to ILDA and import them into LSX (or one of a few of Pangolin's products). The pro version of LSX is only US$375.99 and has a LOT more functionality than MIII. LSX works with a variety of DACs including Medialas'. (I have five Medialas DACs that are still running just fine with LSX.) Oh, and I don't believe Innolasers/LSX has ever charged for an update.
All of this said, MIII is easy to use, being maintained and updated currently, and quite reliable in my experience, so if that product works better for you, then great.
-David
P.S. If anyone wants a copy of Mamba 0.9x including all its bugs, I have an extra copy I never used that I'll let go CHEAP. PM me if interested!
"Help, help, I'm being repressed!"