so far I'm very much enjoying it. it's very Mario and controls just how you'd expect. Mario feels pretty weighty but very snappy. the Wonder Flowers really make things crazy and do a good job of changing things up, and just being silly/fun.
I only got Elephant Mario so far (a lot), no Drill Mario or Bubble Mario yet. Elephant Mario is fun and has some interesting abilities. got Fire Flowers as well, but nothing new there. I'm taking things very slow and revisiting stages when I miss stuff. I'm still on the first world but the map is branching all over the place, so that's cool. nice variety of stages, little challenges, etc...
lots of new enemies, some behave similar to old enemies while others feel very unique to the series. I have to say, watching trailers the new location and enemies seemed weird, but once I started playing that all melted away and it just felt and seemed normal and great.
I've died a few times, but I can't say that anything was difficult so far. I did see one stage that I haven't tried yet with a difficulty rating of 4, whereas everything I've done so far was a 1 or 2, so maybe I'll check that out to get an idea of just how hard it can be.
got a couple of badges, they do a good job of also adding/altering abilities that you can use while playing, and I'm sure different badges can completely change the feel or approach to a stage.
finally the visuals and sound are to die for... it just looks so amazing and sounds so fun. I really love what they did with this game and I'm sure I haven't seen the real good stuff yet! oh, and I really like the new Mario voice, though Mario doesn't really speak outside the occasional "Wahoo" and "Wowie Zowie"
I haven't checked out any of the online yet, but I plan to check it out at some point today