MadLordOfMilk
First Post
I, personally, think it's the best D&D rules system out. It's the game system I primarily play 
(Well, OK, I tend to stick to the Moldvay/Cook/Marsh basic/expert books, but they're close enough to the Mentzer books to be more or less the same)
If you want to check out more or less the same rules, check out the retro-clone Labyrinth Lord, which clones the Moldvay Basic/Expert books. Dark Dungeons clones the 5 Mentzer books/the Rules Cyclopedia, but it includes things like weapon mastery/etc. by default which isn't quite as straightforward as playing with just the red box.

(Well, OK, I tend to stick to the Moldvay/Cook/Marsh basic/expert books, but they're close enough to the Mentzer books to be more or less the same)
If you want to check out more or less the same rules, check out the retro-clone Labyrinth Lord, which clones the Moldvay Basic/Expert books. Dark Dungeons clones the 5 Mentzer books/the Rules Cyclopedia, but it includes things like weapon mastery/etc. by default which isn't quite as straightforward as playing with just the red box.