Linux Mint KDE is another quality KDE distribution that you can choose from. It's actually based on Ubuntu which will still give you access to those repositories giving you easy access to installing software that you need. It's what's called a community edition meaning that volunteers actually put this distribution together. Usually it's a version behind the main version of Mint but still has everything you need.
Linux Mint KDE has a basic desktop that is already customized. It's coming with a fresh blue look to it with the default KDE gray title bars. It's set up quite a bit like Windows with the "start" button the bottom left, a basic taskbar, notification icons, and a clock. It's your standard KDE layout for those who know what this look like.
It uses the new KDE 4 with the plasma desktop. If you are using the KDE edition of Mint, then you probably love the new plasma and do not mind the extra resources that this uses over the old KDE 3. There are many who are split on the differences between the two but users have gradually accepted version four's changes.
Some wonder why to use Mint's KDE edition over something like Kubuntu since both are based on Ubuntu. Linux Mint comes with proprietary drivers installed to play music, dvd, flash, and java. These do not have to be installed by you at all unlike Kubuntu. By default it also uses Firefox and Thunderbird instead of the traditional KDE browser and mail programs. Mint also has some features like MintInstall and MintUpdate. These will help you get new applications installed and updated really easily.
If you do not like the KDE edition, there are also Fluxbox, XFCE, and Gnome editions of Mint to try out as well as other distributions that use KDE.