For the 2.2.x branch the API was created to isolate geotools interfaces from implementation.
For the 2.3.x branch some modification was made to support the use of Expressions against more then just features.
Here is what the module can tell you right now about GeoTools:
- Any "FactoryFinder" or any geotools "glue" code that covers for lack of consistency
- Code that patches the API usability - such as DataUtilities