It's not great, but not bad.
This isn't my favorite show, a lot of violence and many instances where innuendo and sarcasm go over the heads of children. However, they do absorb things and sometimes repeat things, so I try to watch this with my son (who is Pre-K).
I let my son watch this occasionally because the "bad stuff" isn't any worse than what I was exposed to in school many years ago and I'd like the change to see him react, and guide him a little in dealing with, the parts I don't approve of.
I like that the cartoon is well drawn compared to some of the "less pretty" modern types of art. I like that there is a lot of teamwork, powerful heroes shown as both female and male, lots of different types of strength, etc. I like that my son enjoys it and will talk to me about how he would have handled a bad guy, or what superpower he wants, or what different characters could/should do.
This isn't my favorite show, but it's not all bad.