I have this exact kit. On/Off work just fine as does brightness. Once you set it to a color though, it can be tough to get it back to the exactly "warm white" it defaults to but changing to other colors is easy.
To be honest, for under-cabinet lighting it is a bit overkill because you may not need the RGB. If you do not plan on doing other colors I would recommend getting a Warm White LED strip (unless you really like the cool white ones), power supply, and then a simple Zigbee on/off outlet for the power supply. A Securifi Peanut Plug works great for this.