So I'm currently watching the Max Heart season, partially to put some closure on when I watched the 1st season years ago and partially to relive through this dork
Opinions of Nagisa have been quite differing in the fandom from what I've seen. One camp believes she's the best cure that can do no wrong (this is usually from purists who love only the 1st 2 seasons) and another camp who think she's a big ol' negative nancy (er..negative nagisa?) that they're glad it didn't become the norm in the franchise.
Since it had been so long since I had seen Futari wa, I couldn't really defend her that much - but from what I remember I liked Nagisa, I thought her character, while harsh in the beginning, was normal 14 year old girl behavior and that she had a satisfying character arc.
11 episodes into Max Heart, I'm glad to say that's still how I feel.
She's goofy, stubborn, well-meaning, a bit of low self esteem, and learns from her mistakes. I said this before in another character discussion, but I like characters that are flawed because that makes their successes that much more satisfying. and it's interesting to watch too.
Compared to say, Cure Heart who is so perfect the narrative has to constantly tell you and revolve around her, I would much rather watch a character who makes mistakes or gains some self-confidence through her experiences
I also like that Nagisa, while more tomboyish of the two, has alot of the typical "girly" traits, like collecting stuffed animals, crushing on boys, and even has a fantasy of baking a good cake.