Seriously -- This is important. Because I'm pretty sure I always want a Layton game in my handheld, and getting one for the 3DS is pretty great. Especially one that holds on the good, and adapts to the platform.
Professor Layton and the Miracle Mask carries forward all of the stuff the series is known for -- deceptively simple gameplay, elegant execution of the overall package, inclusion of fun characters, and tons of engaging puzzles.
The cut scenes are just pleasant, engaging little things, and until Ni No Kuni comes out (soooo soon!), this as close as I get to playing a Studio Ghibli game.
The shift of exploration to the top screen while keeping navigation on the bottom touch screen works well. I wasn't looking forward to it, but I don't notice it all, and think it makes exploration more engaging for the handheld.
I'm not a fan of the title's in-game polygonal cut scenes -- I prefer the animated ones. And I enjoy the voice acting, so when it's gone in some 2D character dialog transitions ... I miss it.
And the 3D? Well, aside from the polygonal cut scenes mentioned above (which don't stand up to the pre-rendered animated or static scenes even in 2D), things look pretty good in stereoscopic 3D. There a handful of graphical items where elements are in a layer that requires careful distance and angle positioning, but these are few and far between (and far less than other 3DS titles). And some of the puzzles actually benefit from the 3D (imagine!) -- Another feather in the cap over other 3DS titles.
Strong recommend for this title. Level 5 did a great, great job, and it's nice to have another Layton title taking up regular residence in my handheld.