The concept is fine and mostly logical. Visuals are really stunning and wonderful. Personally I think that after Avatar, 2.0 have that 3D visuals. I've seen lot of reviews that says first half is unusually long, which is true but that's the build up of the story, like in the first Robot movie we see the first half as introduction to Chitti and his capabilities while second half consist of the main plot.
In 2.0, especially in the 2nd half, there could have been a lot more, I wanted to see more of Akshay Kumar performance, just one scene and then straight to the 30-minutes climax.
Overall, the concept is all about imbalance caused to nature by humans for their greed which will eventually lead to some disaster. In the movie, Akshay Kumar played that disaster and scientifically termed as the 5th force. We have Chitti to save the day. But we should realize what really going on, what we are causing and what can be the bitter consequences.
Overall I'll rate this a 7 out of 10.