What is your opinion on Firestar?

Agreed I love him forever until the end. Sure he did do some dumb stuff, but he's still the best

I liked him in the first two series, but then he just started going downhill. His constant rhetoric of "we need to help each other!!" and constantly getting into the Clan's business even when they didn't ask for it got so old so fast.

Neutral.

He's not my favorite character, but I don't hate him either… He's not Mary Sue in the way that he was never punished or always perfect, but at the same time I feel like his flaws weren't examined enough or given enough consequences as compared to some of the other characters.

For example, there's Graystripe, who makes a grave mistake of getting into a forbidden relationship without caring about the consequences, suffers by watching his mate die, effectively ostracized from his friends and family, tries to fit into a new group but can't, and at the end is forced to go back to his original home and re-earn and his friends’ trust.

Firestar’s biggest mistake, on the other hand, appears to be when he and Graystripe to an enemy clan (if I remember correctly, since it's been a while since I've read the original series). And the only punishment seem to be being treated like apprentices for a short time. Of course, there was also the whole incident with Yellowfang, but that turned out to be a good thing.

And there are times when he doubts himself, or is reminded of how young he is, but it just seems to be there, and not really slows him down. And then there's the fact that he's out of focus for most of the rest of the series, so there's almost no more development for him.

Overall, I think the Firestar is kind of a cliché character rather than a Sue. He has special origins, a prophecy around him, achieves the highest rank of power a cat can get, knows a special move (his trick of playing dead, which works on many different opponents, and doesn't seem to be known by anyone else), and seems almost be a prodigy (being made a warrior and deputy very early, mentioned to pick up things rather quickly). It makes him perfect for the typical hero role, but not interesting outside of it.

I think Firestar would be more interesting if his flaws or doubts were explored in more detail. For example, what if he starts making mistakes because he's young and immature? What if someone didn't respond to his technique of playing dead? What if someone took advantage of his kindness? Those are all things that could've been done with him to make him a more varied character, but were not (again, this is only from what I remember, so someone correct me if I'm wrong).

And what if there was some way to include some sort of development for him and in other books? Maybe include a chapter or two from his point of view about the forest being destroyed or his daughters leaving. Just to show a different side of him.

Overall, I think he's fits the role that he was meant to play very well, but it doesn't necessarily make him an interesting character. Hence, my feelings are mixed about him.