Now what about this anime?
Katekyo Hitman Reborn (KHR in the future) overall is a good anime, hence the 7 points, but it could be better if not some serious flaws in the story, art, characters and overall setting of the story.
I have not read the manga and this review is not about comparing the two.
Story: Well story was pretty basic. An underdog that undergoes a lot of training to become a hero. There are people along the way that join his family, they fight etc. Simplicity is not the problem of the story, but the way it is given to us. More often than not the story boils down to the inability of some main characters to do simple things, to come up with valid strategies to defeat enemies.
As far as I know there are no fillers in KHR, but there are a LOT of recap episodes. Episodes where some character or the other is telling the whole story-arc from the beginning to another character.
While this plot device is meant to educate people who are jumping in the middle of the show, it is very annoying to people who actually followed the story through and through.
You can skip the recap episodes now, that it is completed, but I cannot imagine the disappointment of people who watched this show as it was ongoing, from week to week.
This anime likes it's Deus Ex Machina plot devices. Last second saves, unusually rapid development of character powers. They are present in the story but not very annoying.
Ending of the anime while complete, annoyed me a lot. Do you remember fairy tales of the old? Where everything would be alright as long as protagonist achieved his/her goal? Well this anime decided that in the end everything can be explained not by logic, but by the existence of... hm... this will be a hard one... I guess MAGIC. Yes, not by science, logic or conventional thinking but the existence of MAGIC can make everything better and you can forget that we just destroyed the time-space continuum theory and every other similar theories JUST to make this ending.
Art: Not much can be said about the art of this anime. It is fairly good. While some fights are not as detailed and thoroughly drawn as, let's say in Hunter x Hunter 2011 or Soul Eater, they still are fairly good and satisfying. So all in all art is good and pleasing to the eyes.
Although when dealing with Mafia story I think anime needs darker settings, not this overly sunny and shiny art form that is given to us. Biggest concern for me was almost total absence of Blood. I mean come ooon even some of the most childish animes have blood in them pleeease give us something to work with.
Sound: Anime has, to my taste, few good op/end songs, but some are really good so it is worth listening at least once and not skipping. Seiyuus worked hard and delivered good performance, not great, but still good.
Character: Not much can be said about characters without spoilers, thus I will be short. For me protagonist was a little annoying. I was annoyed by the way he thinks till the very end of the anime. Of course there are times, like in a fight when he is more linear protagonist than not, and because of that the annoyance is gone but that is for a short while, so all in all protagonist for me was annoying. On the other hand antagonist of the last ark lacks a little sense. I can understand WHY he does what he does but we have absolutely NO BACKSTORY as to what changed him from what he was to what he is.
Enjoyment: Well despite the great black hole in the plot that for me is the ending, I enjoyed the anime Very much. This anime knows it's serious moments, but sometimes overplays it, know the funny moments, but then again sometimes they are very overplayed. First 20 episode for me were very hard to watch. I thought HOW can you take the idea of Mafia story and make THIS out of it, but there were times when faith was restored in this anime.
Overall: I think this anime deserved 8 overall but the serious problems of the story and character development just got in my way to giving this anime more than 7. Yes, as I said, I enjoyed this anime very much, but still it was sometimes too predictable and too annoying to give higher score.
My personal opinion is that this anime is totally WORTH watching. Even with the problems it is very enjoyable and a good way to spend time.
