I think the big reliance on coins could make it an interesting, at least somewhat unique experience compared to past NSMB games. I'm questioning how big of a role they actually play in the gameplay, though. What, does Bowser have some sort of machine or plan or something, and the only way to foil it is by collecting a buttload of coins? Do you unlock new levels with a bunch of coins? Why are coins such a big deal in this one? That was what I was thinking.
I think having to stop to collect billions of coins every 4 seconds would interrupt the flow of the game moreso than any other Mario game (especially with Mario's stupid slide he's done ever since NSMB).
I also notice 100 coins still gives you a 1UP. So... 70 lives at the end of World 1?
Lastly, if this is all about coins, presumably there will be leaderboards. Maybe leaderboards for individual levels, but I doubt that. It'll be total coin count, and then you know it'll be broken within a week because someone will find the level with the fastest opportunity for the most coins and play the level over and over and over.
I've noticed that NSMB2 is already following a trend set by MTO: the point system not relying on skill, but on how much time you can sink into the game. Like, yeah, I had several matches with the regional top leaderboard guy "Dragon:3" (82,391 points) on Mario Tennis. I've beaten him 5 out of the 7 times I've faced him. [darn].... is it because I'm insanely good? Not really, he's a moderately decent player; he just does nothing but play Mario Tennis. I could have 82k points too if I did nothing but play. So, same sort of thing I see happening with NSMB2: You'll find leaderboards that won't show level times completed or anything worthy of achievement (and forget statistics), but it'll show total coin count, probably show the top 30 people (or hell maybe just the top guy and that's it like Mario Tennis) and his coin count will be 7.4 million coins.
EDIT: (and for the love of Christ, get rid of the stupid ass BAHH BAHH voice bull[dukar]. I thought they were gonna kill it off, but it was everywhere in the NSMB U trailer)