allow switching of users, like drive.google.com does, and, ideally, allow multiple tabs with multiple users.

I have 4 Atlassian accounts, 3 for different companies I work for, and one private. I am constantly switching between them. This requires logging out, and logging in which requires finding and entering my password for that account several times a day. What a pain!

Also, you can only have one account open at a time, as your auth cookies are browser wide.

The way google drive works is that that you can add your accounts, and then pick any of them from a dropdown. Most of the time, you cont need to authenticate again. Much more usable.

Also, you can have two browser windows open with two different users. This would be a huge benefit for using bitbucket/altlassian products.

Currently, I use Bitbucket for some accounts, and GitHub for others, as it means I can have both open at the same time with two different users.