The toolkit is very small and lacks good definition of elements (both visually in that it lacks contrast, and practically in that I have no idea what is clickable or editable).
The page structure isn't that clear either, where are the column headings? And on my widescreen browser window the isn't a limit on horizontal stretch - I have to play with the browser to find a good width. Also, I can expand code, but how do I shrink/hide it?
And no, you can't shrink/hide code, other than by re-diffing. What can I say -- it's surprisingly hard to implement and didn't seem worth it.
GitHub: 31M users
BitBucket: 6M users, 1M orgs
GitLab: 100K orgs
The GitLab number tallies with Emily's answer, which gives me some moderate confidence that these numbers are in the right neighborhood. I'm also going to assume that the users-vs-teams numbers are all in roughly the same proportion.
Based one these numbers it doesn't make much sense to target BitBucket unless either 1) they're growing much faster than GitHub (unlikely) or 2) their customers are a much better fit for Reviewable (possible, but it would have to be a truly significant difference in userbase composition). Targeting GitLab doesn't appear to make sense at all (as a business), though perhaps they're growing fast.
https://marketplace.atlassian.com/addons/app/bitbucket/top-s...
Is what makes me uncomfortable about modern webdev. Valuable product work constantly deprioritized by migrations to new frameworks. Magpieing has always been a risk in hobby projects, but in the past there was a smaller torrent of nee things to always be migrating to.