Without question Linux Mint as it offers the complete package without being tied down to endless agreements and offers complete freedom to do with as you wish. Additionally Linux Mint benefits from sourcing software packages from the massive amount of Ubuntu repositories which contain an endless amount of useful software
I currently have 3 Linux Mint releases either installed or on custom LiveDVD created using Remastersys http://www.geekconnection.org/remastersys/remastersystool.html
Those releases being Linux Mint 6 Linux Mint 7 and Linux Mint 8
Linux Mint 6 Download
http://www.linuxmint.com/edition.php?id=31
The Perfect Desktop - Linux Mint 6 (Felicia)
http://www.howtoforge.com/the-perfect-desktop-linux-mint-6-felicia
Linux Mint 7 Download
http://www.linuxmint.com/edition.php?id=38
The Perfect Desktop - Linux Mint 7 (Gloria)
http://www.howtoforge.com/the-perfect-desktop-linux-mint-7-gloria
Linux Mint 8 Download
http://www.linuxmint.com/edition.php?id=44
The Perfect Desktop - Linux Mint 8 (Helena)
http://www.howtoforge.com/the-perfect-desktop-linux-mint-8-helena
All of these have been heavily customized in one form or another and offering features that are not included on the standard release
LUg.