the biggest one was Skarra, who I remember hating as a kid (I thought he was wishy-washy and weak), but as an adult I have a lot more sympathy for the poor kid.

I didn't read The Firelings as a child; I discovered it in college and Skarra was my favorite character when I did, possibly because he was having the hardest time figuring out how to be a person. Life is the character I really want to re-read for, because she's so spikily messed up in ways that now feel slightly ahead of their time for children's/YA literature—I remember in particular her suspicion and confusion when other people don't behave badly, which she is always trying to pigeonhole into selfishness or weakness so that they'll make more sense to her. (The example that seems to have stuck with me is when she insults Tacky-obbie's uncle's pots: Tacky-obbie doesn't defend his uncle; she scolds him for being a "truckler," never standing up to anyone; Tacky-obbie points out that his uncle isn't a good potter and it's no shame for him to admit it; Life has no idea what to do with this interaction.) She has emotions about discovering that Skarra isn't just weird and nervous, he's as plausibly damaged as you would expect from someone who has accepted a daily diet of emotional and physical abuse since childhood! Her ability to deal with said emotions is almost completely crap! And yet it's actually good for them to know one another, in their painfully awkward, desperately ironic ways, which I feel another novel might not have attempted or succeeded at. I agree with skygiants that its sympathy for its characters is very take-it-or-leave-it, but I suspect that's one of the reasons it works so well for me. It doesn't feel heavy. I didn't notice for years.