I have to admit toward the end I was getting bored with the grind. Since my alts are all different careers and on is a Klink in a way I am excited to be working on them.
Klingon is pretty boring, I'd have never gotten mine to the max level so quickly if it wasn't for the level up weekend. Even with the bonus exp I had to run the weeklies so often that it took out all fun of them.
Klingons do have several unique and really good missions though, especially when Qo'noS is under attack. I really enjoyed that mission chain. (I hope I didn't give too many spoilers.)
For my Klingons I'll mostly wait till more content becomes available before leveling up more characters there.