Since 17 or so it's seemed extremely stable to me. It also tends to have drivers for just about anything, but that's also true of Ubuntu. It is sort of configured for Linux newbies, but it's also configured to just be A Desktop with as little crud as possible, besides that necessary to maintain its broad compatibility and ease of installation.
Its popularity came around the time that Canonical started doing things like inserting a 'shopping lens search' into default installations' desktop UI, pushing insane and bulky window managers, bucking Wayland to make their own X replacement, and generally making people uneasy about their monopoly on 'easy' Linux OSes.
So Mint is a solid 'No-Frills Give Me A Linux Now' installation. Sometimes you don't want to spend hours tinkering, okay? The last time I installed Fedora (21 and 22), it was consistently a ghastly, slow and buggy nightmare that approached a stage 3 Gentoo install by the time something functional was up and running. I was floored at how bad it was on such a popular distro, and once installed, it was also a lot of effort to get simple things like yum working properly. It could have just been me, but this was fairly standard hardware; I came away with the impression that it was not even close to an easy or pleasant install experience for a broad range of users, and nothing I'd be interested in using again.