I loved Yii because it was similar to .NET development (as framework), it is very OOP and applies formal technologies very good (like OOP, MVC, etc), it's really stable and it's perfect for a corporate environment. Yii includes very good tools to reduce development and lets you …
Yii is very well suited if you love to program with Object Oriented PHP. This framework uses OOP very well and if you know this pattern you'll love it. The same applies for its MVC architecture and if you come from formal software development education. Also if you are in a bussiness enviroment and need a stable framework. This is the tool for you. It uses very formal scheme but I would like more open and hackable framework, and for this Yii2 is not a good option. Also, if you like to have bleeding edge technologies I don't recommend this framework.
I think is really easy to use, it's not perfect but many developers with great experience will know how to exploit this framework to create great apps!
It's has a really good support based on online documentation and official forums. But sometimes I wish there were a paid service where to report some urgent issues.