Linux Controversies of 2011: Linux Mint is the Most Popular Distro
From the 'Top Controversies of 2011' files:
The decline of Ubuntu and the corresponding rise of Linux Mint is one of the bigger Linux controversies of 2011.
Ubuntu's introduction of Unity alienated a non-trivial portion of the Ubuntu user-base which then went looking for a new home – and found it in Linux Mint.
How big was the exodus from Ubuntu to Mint?
That's difficult if not impossible to accurately measure. Plenty of 'experts' liked to highlight the 'fact' that Mint is the top Distro as ranked by Distrowatch. Distrowatch however is not a measure of users or even downloads, it's just a measure of the relative popularity of a given distro's page on the Distrowatch site.
It is likely that Mint has picked up a good number of former Ubuntu users. It is also likely that Mint's popularity surged in 2011. It is not clear and also not entirely likely in my opinion that Mint is the most popular distro in terms of total number of users.
That doesn't mean that Mint isn't a great distro, because it is. Mint developers respect the tens of thousands of Linux desktop users that want and/or need a more traditional GNOME type experience. This is a controversy brought on by the vehement dislike of Unity and the lack of sensitivity from Ubuntu's leadership about its shortcomings.
In 2012, with Mint now moving a new direction with the Cinammon desktop, expect to see more 'Mint is the best' type hoopla in the New Year.