That question has a different answer depending on the value each user gives to the new features. I don't think there's a universal answer. The value for money for each feature depends from person to person.

If you have lots of money, it's worth it. If your cash is limited and you can live without the new features, don't upgrade. In the middle there's a big grey area.
In my case it was worth it because of the new clouds and the new infinite terrains and the water editor but only because I had some available cash to spend. If I hadn't, I could live happily with Vue6 for a few more years...