The real answer, of course, is new power and revenue enhancement. *mwa-ha-ha-ha-ha*

Nuendo, Cubase's big brother, is a complete AV production suite comparable to Sony Vegas. They manage to come up with enough enhancements that every couple of years they can charge $1500 or more for an upgrade to the latest and greatest version.

Many of their improvements have to do with taking advantage of processing power. Since version 2 users have been able to run it on networked PCs. Now that an individual machine can have 64 Gb or more of RAM I'm not sure that's necessary, but more is always better, right?

Another thing is being able to handle new file formats. There's always something.

I'll have to ask a friend, a dedicated amateur who is currently on version 4, what makes him keep at it. I know that between versions 2 and 3 they changed their sequencer file format to something that wasn't backwards compatible, so if you were transferring files with friends or co-creators who upgraded you had to have the new version. I do know that it is an extremely stable and robust DAW. Has to be when you're working in a professional production environment.

"My primary musical instrument is the personal computer."