[damianh]

How does one launch a profile from the about:profiles page? ;)

It's a concept that is first class supported and easy to use in all othe browsers. There is just a ton of usability issues across the board, even with the third party addon.

[account-5]

I suppose it's just what you're used to. Once you're at about:profiles you're presented with a list of profiles to open and options to create new ones. Fairly simple to use, though from other comments not as obvious as other browsers.