17.1 Rebecca is the latest release of Linux Mint. Unlike previous version 17.1 will not be based on the latest rendition of Ubuntu. Rebecca will not be based on Ubuntu 14.10, it will use 14.04 and it will continue to use it for the next two years. Like Mint 17, 17.1 will have Long Term Support (LTS) and will continue to have updates for it until 2019. Not only will you receive security updates but you will also get application updates and even power update to the latest Linux kernal.
I have only tested the Linux Mint 17.1 using the Cinnamon desktop environment therefore completely unfamiliar with the Linux Mint KDE or Xfce. Cinnamon works great on modern computers with sufficient amount of RAM and video RAM. I suggest Xfce for computers that came with XP.
Rebecca is a big step forward for Mint. I can’t wait to see how it works out.