Played through the first world in about 17 minutes, difficulty was at level 20. I was breathing heavy by the end, those squats were murder on my knees, haha. I can see myself using this daily to get in a regular regimen before adding other exercise outside the game itself. I don't do much exercise, and I haven't done yoga in over a year-and-a-half so it took some getting use to the exercises.
Game is a lot of fun, only issue is needing the ring-con and leg strap on before being able to go through the menus, made doing the multi-task mode a chore since I needed to put the leg strap on every time I wanted to check where I was at out of 500 total. Another problem is with the multi-task mode, not sure what I'm doing wrong, but it feels like it's undercounting the amount of presses I do, I'm doing them slow and deliberate, not super fast, and when I counted to 20, it only counted 13. I eventually quit after 221/500 because it was taking way too long. Spent the better part of 45 minutes and only got that much. Other than that it's a lot of fun. The age-ranking is a nice touch. Hope they update the game to allow joy-con menu navigation without the need for the ring-con/leg strap.