Terrible script, unfunny puns every 30 seconds, etc, etc...but....
...The fight between Dutch and D'Avin was extremely impressive. I'd say it was more convincing than the majority of shows like this (Nikita springs to mind, which didn't have a convincing fight scene in 3 whole seasons).
However, unfortunately, this can't save the show. I find the characters superficial, their motivations unbelievable, the camera direction odd at times, and the relentless, overbearing, soundtrack (a clumsy device used to make the drama and action seem more exciting) destroys any subtleties that may exist in the acting.
I suppose it's good to see a familiar face in Aaron Ashmore (from Smallville), and he does a good job with what he has to work with, but it doesn't help much.
At halfway through episode 8, I imagine I'll ditch it at the end of this season.
I much preferred Dark Matter, because the script was much more naturalistic and I was intrigued by the mystery. The cast was strong, and there was a good mix of varied characters. Instead of the constant, silly, puns, they had a limited number of well-executed humorous moments throughout the season. The soundtrack was a bit of a problem for me too (no light and shade), but at least it wasn't ridiculous like Killjoys.
Unlike others, Killjoys reminds me of Firefly, which I found one-dimensional, and Dark Matter reminded me of (a very simplified) Farscape (obviously, it's almost impossible to match Farscape!)