I lasted almost a year with Linux Mint, but I've now gone back to using Windows 7 on my main desktop PC. There isn't really a single reason for this, other than that I felt like playing a few games that I'd bought years ago (the likes of Sid Meiers' Railroads and Settlers 2). The purchase of a 1920x1200 monitor and a new processor (with decent onboard graphics) means that in theory I can enjoy the full potential of these old games (although of course, the HD Graphics 4600 of a Haswell processor won't manage many modern games at that resolution). Colour calibration is a lot easier with Windows 7 too.
So would I go back to using Mint? Almost certainly, yes. It has a few foibles and irritations, that's for sure. Being based on Ubuntu rather than Debian (more of that in a moment) means that it inherits a fair bit of baggage, and being unable to upgrade versions is a pain too (you can easily do it, but a clean install is strongly recommended). If I go back to Mint, it will probably be the semi-rolling Debian distribution.
Is it a credible replacement for Windows 7? Definitely. I could achieve everything I wanted to achieve using Linux Mint, except playing certain games, and I could probably have made those work using WINE if I'd tried. In fact, I'd go so far as to say that if I was given a new computer with Windows 8 on it, I'd replace it with Mint without a second thought.