Games for Old-school Dungeon Crawling

I've put together a quick summary of three retro style games that I think work best for old fashioned dungeon crawling.  This is just designed to highlight their similarities/differences and is in no way intended to be a review or criticism of any of them.  I've placed them in alphabetical order so as not to indicate any preference by order.

Castles & Crusades

Overview:  A D20-light version of AD&D.  It follows a number of the current D20 conventions, while trying to stay rules-light.  There are no skill lists, just class skills.  Armor class is handled in the modern ascending format.  It is a race/class based system with all classes open to all races.  It's rules-light in today's terms, but is less a retro clone than a pared down version of D&D 3.5 with AD&D sensibilities.

My Assessment:  Probably the best choice for 3.5/4e players looking to scale back the complexity of their games while maintaining some familiar connection to the rules that they know.  A good game from a good company, but the most complex of the games discussed here. 

Labyrinth Lord  

Overview:  A retro clone of the Moldvay/Cook Basic/Expert D&D rules from 1981.  Race and class are not treated separately.  Dwarves, elves and halflings are their own class, with dwarves and halflings basically being fighters and elves being fighter magic users.

My Assessment:  A great choice for folks who cut their teeth on Moldvay and Cook and are after a classic dungeon crawl experience without a lot of overhead.  A nice complete package and free to boot.

Swords & Wizardry 

Overview:  This is for the most part a cleaned up, better organized version of OD&D (Original D&D).  It actually comes in two flavors, regular Swords & Wizardry and Swords & Wizardry White Box Edition.  The regular version includes that later stat bonuses for strength and dexterity and constitution , while the white box version retains the original idea that only charisma has any direct bonuses.  Demihumans are, in keeping with the OD&D rules, more limited in level progression than in Labyrinth Lord or Castles & Crusades.  

My Assessment:  Jump into the wayback machine and see how the grognards played D&D back in 1974-79.  Probably the best choice for people who want to house-rule their games a lot.  The rules found here adhere most closely to the old-school "guidelines" approach.  The Erol Otus style cover of the regular edition and that it's freely available are pluses too.