Guilty Crown is a series that I recently watched, and my feelings about it come off as rather mixed.
The first 12 episodes of this series are really good. They follow a very similar plot to that of Code Geass, so it is enjoyable by a lot of people. The Animations are great, the Sountrack is just wonderful and the characters are all really fun and well designed. If this series had of been made as a 12 episodes series and ended there, I think I probably would have given it a 9.
As the series reaches its second half, it seems to much like a Code Geass ripoff. Now, I'm not trying to point fingers (Well, I just did. But ignore that.) but from the begining it had a very similar setting and plot to Code Geass, a Boy meets a mysterious girl, gains a superpower that allows him to join a group of terrorists and fight against a foreign nation that has entered their own and is treating Japanese citizens unfairly.
Shu's power, known as "Void" allows him to draw weapons out of people. I know this has been done before, but I think in this series it was rather unique, just seeing the vast amount of weapons that appear in the series from this Void ability, not to mention the stunning animation that goes along with using one. Speaking of animation, all of the fight scenes are very well animated, and felt somewhat refreshing to watch.
A main gripe I have is the Mecha being all CGI. I'm not a fan of CGI mecha, and it at times looked out of place in the series, but not so much it will make you stop watching. The Mecha action in this series is also somewhat limited, but its also not a main selling point for the anime so that is forgiveable too.
The Terrorist group, "Funeral Parlor" is full of interesting and fun characters, each one of them playing an important role in the story at some point or another. None of these characters ever came off as boring to me despite my initial impressions of them.
Like I said, a major downfall with this series is that while the first 12 episodes are very good, it really goes downhill from there. While it does pick up in the last few episodes again, I actually started wondering to myself if it was worth finishing at some points. The series left me content however, and wrapped things up nicely. While there were a lot of things that were unexplained in the series and with the ending, I think it still was enough to finish it.
I reccomend you watch the first 12 episodes of this series. Then choose where to go from there. If you want to watch more, go ahead. You probably won't lose anyhting. Except interest in the series. Its an enjoyable series, but by no means a masterpiece.
It also had a Great set of OP/ED's. Just thought I'd mention that.