The design itself is practical and clever, a modular approach has been taken to allow for adaptation and expansion. This way you can easily expand to fill larger windows by adding additional beds, or expand and rearrange to meet the needs of different spaces and goals.
Each bed has drainage holes on the bottom and a flat panel on the base. They can be joined using the 8 x 4 walkway. The central walkway has arches to accommodate for the drainage holes and is not fixed in any way, allowing for it to be easily removed to mop up any spills. There shouldn't be many though as you only want moist seeds and not water logged ones :).
The shed fits onto one of the beds, so it is optional and can be used anywhere. It has a removable roof making it a great place to store seeds.
Also there are mini green houses that can be used as a cloche to promote germination. Again these are modular and can be added additionally.
Over all it has a lot of scope, and can be customized to fit the owners needs for productivity or just for fun and looks. There could be additional sets with different designs and expansion packs to add more beds, or more garden helpers.