Intuitive and Documented
It is strongly influenced by jquery with many similar methods so you'll feel at ease developing with Umbrella.
However there are also some improvements such as with .ajax(), .append(), etc.
Tiny and Clear
3kb when gzipped means it will load in a snap on mobile. The core is reusable so new features are also tiny.
Tested and Performant
The speed is similar to jquery and there are many tests, including performance ones.