The TL;DR of the rule is:

The 6 classic ability scores are (allegedly) not well-balanced among themselves. So the attempt is to fix that by:

• Combine Strength and Constitution
• Split Dexterity into 2 (basically, Dexterity: the stuff with your hands; and Agility: the stuff with your feet and body)
• Charisma becomes the stat for Will saves, instead of Wisdom

In short, do you agree with the stated goal of the system? Whether or not you do, do you think these particular changes are a good way of addressing that goal?

Have you ever tried out this variant, how does it go in practice?