That's the thing - Crowley's original role was a plot device in Season 5. But given Mark's charm with the character, the writers expanded Crowley into something a lot larger. After the last trial he's lost everything he's built up the last three seasons and now he's a demon who craves his lost humanity. I look forward to seeing where they take him.
As for Abaddon....she's yet to grow on me
Thats fair, so far she's been nothing more than a demonic bulldozer that reset the rules on how to deal with demons. She has no where near the charm of Mark's Crowley, but she'll definitely have an impact on things to come for the next two seasons.