I haven't seen a good name for "2nd generation clones" - games that use the OGL to mimic elements of D&D, but aren't creating a faithful retro-clone of the original rules. So I'm going to start calling them Sequels, at least until someone smarter and wiser comes up with a cooler name (and no, not 'fantasy heartbreakers'). The sequel games I'm most familiar with are LOTFP or ACKS. LOTFP goes lower magic, grim and grittier, with stronger character archetypes (niche protection), weirder magic, and a consistent skills set. ACKS isn't even published yet, but it's looking really good. It introduces a very strong campaign play mode that includes campaign roles for the core classes, domains, economics, and mass combat. The class design approach mixes in some 3E style elements and might bridge the generation gap between new schoolers and old schoolers. (I'm equating D&D new school = class customization and optimization).
True clones are things like Labyrinth Lord (BX D&D), OSRIC (AD&D), Swords & Wizardry (original D&D), and Dark Dungeons (Rules Cyclopedia/Mentzer D&D).
I don't know if it's nostalgia or comfort, but I find myself using different copies of the original rules as my primary references, and using the Clones or Sequels as a source of house rules. 30 years later, I still love the blue and red basic and expert books. I can find things much faster in BX or the AD&D books than LL, for instance, although publishers are starting to move beyond basic publishing to usability at the table and layout - so my primary table references could change. I have a hard time imagining using old-style thieves after using the LOTFP specialist - I also love the LOTFP encumbrance system, the skill system, and the focus on the fighter. I've been getting all the prerelease rules of ACKS, and can see I'll be retiring my Companion domain economics (among other things) once ACKS comes out, and play testing their own fighter tweaks. I foresee my home games will be a mish-mash of systems going forward.
Seemed like a good idea for a poll. Do you primarily run a purist game (Original Rules only), Original Rules with your own house rules, a Clone, a Sequel, or a Frankenstein mash-up of everything?