After years of Coffee, why Kool-Aid?

I left the original D&D and AD&D behind years ago, before either was actually discontinued. The reasons were many. So -- why return?

To me the Old School Renaissance is not about playing a particular set
of rules in a particular way, the dungeon crawl. It is about going back
to the roots of our hobby and seeing what we could do differently. 
- Author, Bat in the Attic

This sums it up a lot of it. As games built on successful commercial models give us more and more, it's interesting to turn back the clock to a time when the hobby was a hobby. But instead of a purely nostalgic experience I have thirty years of gaming experience to bring to my re-examination.

One of the things I am enjoying about Adventurer, Conqueror, King is that it is not just a retro-clone, it's a game that starts as a clone but adds a simple proficiency system, and a complete domain  system, becoming much more than a reprint of BD&D+.