The article at Karmaburn does a good job at forming the correct set of mind:

Others offered some complaints about Nodame Paris, mostly regarding the new characters (and absence of old ones) and the look of the 3D orchestra. These issues don’t bother me because my primary interests surround Nodame herself.

Sadly, I don't know if his efforts help me. My complaints were not primarily about the 3D, although I mentioned that too. The biggest problem was the story, simultaneously crumpled and aimless (in such a short series too). Characters were the second biggest issue. Here's Evirus' reasonable take:

I’m okay with new characters. It’s better than keeping the original cast around forever and adding more and more new characters with each succeeding episode, diluting the screen time for all of them. StrikerS, I’m looking in your direction. Plus it wouldn’t make sense for Nodame to feel homesick if everybody she knew in Japan happened to follow her following Chiaki to Paris.

What he's saying sounds right, but the problem is: new characters sucked, at least in the beginning. The only one who I could stomach was Ryu (the second edition of Kyora in a way). Maybe it gets better later, but sadly Frank and Tanya poison the well early on.

It is nice to see [Nodame's] relationship with Chiaki has advanced. These are baby steps to be sure, especially if they’ve known each other four years already, but by anime standards they are leaps and bounds. At least they’re officially a couple now.

They were a couple in the original Nodame already:

What Paris-hen is doing borders on a reset.