This is an interesting kit, but it is incomplete and some parts are incorrect. The chassis is cut for a different project, and does not have the correct mounting points for the controller board or the sensor, so additional drilling is required. The instructions are incomplete - for instance there is no reference at all to the sensor assembly, which is quite complex. There is no wiring diagram, so a good knowledge of Arduino add-ons and power supply arrangement is required. There are 4 stand offs supplied, but there should be 12. Some soldering is required, as well as additional tools. Dupont connectors are not included.
On the plus side, the sensor mount is actually a tilt-and pan mount for a camera, and can be upgraded with some readily-available extras. The castor has ball bearings. The sensor shield includes headers for a number of additional components, including a LCD display, SD card and Bluetooth (but note that the Arduino might not support all functions simultaneously).
The encoder wheels are provided, but to get feedback on the number of steps for each wheel (for instance, to ensure straight-line tracking) you will need to add the opto sensors and create the required code. There are cutouts on the board for mounting the sensors.
This is a simple robot that is a good basis for Arduino-based robot control, but be prepared to deal with the problems mentioned above.

Fun to build and works great. I built this kit as a working obstacle-avoidance robot car. Provided my own wires, standoffs, and some additional hardware. Also had to drill some additional mounting holes. I switched to using five AA batteries to get better voltage regulation.