I completed this ages ago, but it's actually quite difficult.
Like many of you said already, games involving the rotating of the Control Stick are quite frustrating. While I didn't find Paddle Battle too difficult, I had trouble with Tug of War and the game where you had to light up a lightbulb by cycling, before a Boo caught you (forgot its name).
And, as VIP said, it's a great way to get all 50 minigames.
While the life system of this game looked good in theory, in practice it was quite interfering, as most of the time, you only got 10 coins for winning a minigame - which means 10 minigames for a 1-UP. At least they were grateful enough to have Koopa Spaces to save.