This is a guilty pleasure of mine, I understand why people don't like it as the realism and strangeness can totally jar with what some people like. I enjoy it as it is a bit of silly escapism, the steam punk nature of the world that they work in is fun and interesting. You follow so many famous characters from different stories and this is possibly another thing people dislike as the author of the original story took existing characters and did what he wanted with them.
I think it works quite well as a bit of fun with some good explosions and scenes, i do think that it get's caught up in it's own importance trying to put meaning and develop character that is not really needed. The actors they got to play the characters were good and as developed as they need to be but like I said there are some story threads that are just not needed and bog the overall fun romp the story is.
I will say this is 4 guilty stars for me, I can watch it fairly regularly and still enjoy it and actually watched it last when it was on the TV.