Personally, I'm not too crazy for Mario's new design. I think it's too faded, as I always imagine Mario wearing bright-colored clothing. Likewise with Peach. Bowser, however, looks pure awesome. Yoshi's more humanoid design sucks, though.
Link and Zelda look perfect. The TP designs are plain awesome, and far more suited to the characters than Melee's models.
I've always hated the Zero Suit - it's cool that they can make a respectable armorless Samus, but the Zero Suit just doesn't work for me. Especially the hair - it makes sense for Samus to tie her hair back, but the style's just ugly.
Fox looks okay. As someone else in this thread stated, it's a blend of the cartoony Command design and the more realistic Adventures/Assault design. It works for him, because a futuristic pilot fox-man should be at least somewhat cartoony.
The Subspace Army looks pretty generic, frankly. Other than the Ancient Minister, they look like someone shopped a few sprites together, then rendered it.