From my 7 year old:
It was fun. I liked all the levels. I liked how after I won all the first levels with Mario, you got to go back and do the levels again with Luigi, but the levels were different. I found Princess Peach. It always kept me playing and not wanting to put it down.
When I play a Mario game I know exactly what to expect which is good and bad. This Mario game was fun and beautiful but so was Mario galaxy. This seemed to lack the creativity of the galaxy series and was extremely easy to beat. It's fun but forgettable as soon as you beat bowser for the last time. Also the items are not that fun and, in many cases, they make the game that much easier to beat. With so many well written and story driven games out today along with well rounded 3ds games such as Zelda and cave story which mixes action and puzzles with a very good story, it's hard to enjoy this game as much as others. It's a good rental but definitely glad I didn't fork over 40$ for this. When they fuse the story and rpg elements from the paper Mario and the Mario and luigi saga with the creativity and exciting platforming from the galaxy series then I'll give mario a 10 but for now this is game is about a 7.
I've been playing this game for a week, and I'm in world 8. Seems to be much longer than that yet, and the worlds are fun and detailed. I immediately remembered why Mario games are so loved, because the level of gameplay and attention to detail is off the charts.
However, there's something wrong with this game when it's left in Sleep mode during the day. It drains the battery completely by the afternoon, even if I haven't played it along the day. Other games haven't done that in the past, so I'm pretty sure there's a big bug in this game that keeps the internals running at full speed even when the screen goes off. That's a big letdown for me, because I don't like to charge my console midday, only when I'm going back to sleep. So, go bark at a tree if you don't like what I said. It bugs me.
Other than that, I like the golden Tanooki mode, that allows you to barrel through everything unscather, and the fly-to-the-pole wing. I thing those were nice additions. I'm sure some fanboys are gonna hate my review, but they can go shove it.