I bought the Variety Kit.
Just so I make it clear, I don't have kids. My girlfriend and I are still kids in our hearts and the whole idea of Labo was interesting enough for us to jump in. For now, I've only built the RC Car and the Fishing Rod ( she's giving me a pass on those and the motorcycle, but we have to do the house and piano together or else... that's the threat she gave me). Overall, I'm surprised by the quality and ingenuity of it. The building process is simple enough so a kid won't be frustrated and also interesting enough for an adult who like creating things to have fun.
The software seems to have enough depth to last a while and each setup comes with instructions on how everything works and suggestions on what can be done if you have a little bit of imaginations (maybe not the fishing game, this is pretty straight forward).
I already had a good idea of how the Joycons are working, but the Joycon manual in the Discovery mode is really interesting to go through. It explains in detail how the the technology inside the controllers can be used and the potential for them is bigger than I thought.
I still have 3 kits to do, but overall, I'm impressed the concept.
I don't think this will sell or have an impact like Wii Fit, Wii Sports or Brain Age had at their time, but this will sell more than some people expect, especially during holidays.