Faiz is the only series I thought was complete crap, don't understand why all the hype there. That is really the only KR series I could not finish.
Kabuto has its faults but it was entertaining, and sometimes that's good enough.
I've only see five episodes of Agito so far, but so far enjoying it.
Kuuga is excellent
Love love love Blade! It's definitely my favorite series.
Decade- I loved, I liked the different takes on previous series, I especially loved how episodes like the Faiz and Kabuto ones managed to condense entire series into two episodes and give you the full story just about. People who say "It don't make sense, there was no story, where are the originals" are mostly just hung up on the world changes, and not paying attention.
Ryuki- was decent, I really didn't dig the ending though.
Den-O- I thought was fun, time travel is one of my favorite themes.
Hibiki- excellent up until episode 30.
Kiva-Alright series, lots of wasted potential though, and you could tell that the writers had no idea what to do with it. Great soundtrack though, best part of the series along with the Armor designs.
Double-Alright so far.