Is this a good starter kit?
Price-wise it is a good deal. Note, however, this kit contains the old version of the hub. If you want to upgrade to full-colour control later on it is better buy the new hub and get the other part seperately. It is possible to combine legacy bulbs and strip controllers with the new hub without problems.
NB, there is no full-colour strip controller available yet. Personally, I am very happy with the 256 colours plus 20 brigthness values. Milight provides, but obviously other light systems like Hue can render more colours. Full-colour gives you the ability to choose from 16.7 million colour values though not necessarily distinguishable.
I need one hub for 4 controller, right?
Yes. Via the hub your’re able to control 4 channels individually. According to the docs it is possible to pair 100+ lights per channel.