I didn't notice anything off about the framerate, but the graphics didn't really wow me (especially when they made it a real advertising point with "Enhanced Graphics!"). Taking a look at that balloon enemy, for example, it just seems completely devoid of... style. Don't get me wrong, the design itself is fine (I would be quite the hypocrite if I said I'm against minimalistic circular designs for characters) but I can't quite it into words why that enemy looked bad... It's a combination of lighting and textures, I think. It just looks like the 3D equivalent of someone making a circle in MS paint and filling it with the bucket tool.

And the animation upon its death is also really delayed and odd.

It's nothing really deal-breaking for me or something I would call terrible. But I can at least see where people are coming from with their complaints