I'm in much the same situation as you: a committed Bibble Pro user, I even shelled out the cash to update to Corel AfterShot Pro. But it seems like Corel isn't giving it the maintenance it deserves; I just ordered a shiny new Canon 6D, only to discover AfterShot doesn't support it yet.
However, that prompted a reevaluation of the options on Linux, which can only be a good thing. Nothing seems to have the features and polish of Bibble yet, but darktable is starting to get pretty nice. It does lack some of the tools that I can't live without though, such as the amazing Bibble straighten tool.
It's nice to have another option, and it does feel like the open source tools are heading in the direction of becoming serious competitors.