The clones just keep on comin'.
Although I have purchased a myriad of OSR supplements and modules, I have only ever purchased two retro-clone core books:
1. OSRIC, economy edition. Elven bucks for all the info of the PHB, DMG, MM, and Fiend Folio (yeah, I like the Folio... suck it) without the yellowed pages and old pot smell of second-hand original books. The real bonus here is that OSRIC is much better organized (well, except for the monsters.) When I ran AD&D, I found that eventually all I needed on the table was OSRIC.
2. Mutant Future- I loves me some Gamma World, but I'm not a huge fan of the old rules. Mutant Future gives me all the gonzo mutant goodness of Gamma World with a rule set that I much prefer and am far more comfortable with. Oh, and it made for some easy (and bitchin') D&D crossover.
I hate to say it, but I really have no use for print copies of Labyrinth Lord, Swords & Wizardry, and that whole gang... I have the original red and blue books, a near complete set of orange spine AD&D 1st ed books, and the mighty Cyclopedia. From where I sit, the differences between the clones are mostly trade dress and a few house rules.
To end on a bright note: many of the clones are free on PDF, which is how I found out that I wanted print copies of OSRIC and MuFu.