Moe had started reading the Swords & Wizardry pdf, and had the following comment on facebook as he was reading:
"I'm finding it hard to see what makes this any different from the other games of its type. Every OSR game reads very similar," and then, later: "Found some bits I did like, multi-classing and dual classing seemed to be handled well. Alignment seems to be based on Mike Michael Moorcock vs. Tolkien (or wherever D&D got their alignment system). I dig the few extra abilities Fighters get. At least I'm finally starting to see some differences."
I happened to be in that sort of mood, so I jumped on the thread with some thoughts. Granted, I created something of a wall of text, but I came up with the following:
Hi Moe, you're absolutely right that the system itself is extraordinarily similar to other OSR games, just because as a retro-clone it tries to reproduce a system that was very similar to the other D&D versions that came out prior to 3d edition. All the retro-clones are highly similar, and then you see the sudden massive shift in the 3E-based Pathfinder retro-clone-method. S&W is to some degree an outlier because OD&D (the S&W source system) had more areas that were basically gaps left for the table to rule, which is why the S&W book has lots of areas where "there's no rule here, but here are some of the historical ways that people ruled it." Initiative is the biggest one of these gaps -- there wasn't an initiative system in OD&D until one of the later supplements. What I tried to do with the book was to (a) codify and combine supplements, (b) present the system in a way that's more readable for people who learned to read an RPG book using the organizational presentation used in AD&D and beyond, (c) provide a pathway for people to begin an introductory game from what is at a more advanced level a welter of potentially-confusing options and gaps, and (d) offer those alternative versions of tested house-rules for when people essentially understand the game and want to try out the various other options. So if you're looking for what's unique in S&W as opposed to other OSR systems, it's actually the *gaps* that are the unique features, not so much the places where there's a firm rule. That's where OD&D really differed from the post-OD&D systems.
Most other retro-clones also have interesting design-backgrounds and author intents. Labyrinth Lord, which is a clone of Moldvay Basic D&D, tries to reproduce an approach that was (at the time) quite the opposite of OD&D -- namely, an emphasis on a more elegant rule-system that was internally very complete. Still open-ended and designed on a concept of a high level of DM fiat, but without the need to house-rule any fundamental portions of the rules (such as initiative). The rules of Moldvay basic, as reproduced by Labyrinth Lord, have a much more defined outer boundary than OD&D, and it was that outer reach where the house-ruling and the high-creativity are supposed to kick in, based on a firm foundation of a well-defined, elegant, clear system. In OD&D, the house-ruling and high creativity are required at the very fundamental level of the essential rules, which is nowadays probably considered bad game design. My "default introductory path" through the rules, in S&W, was intended to help people jump the gap over the vagueness of the basic rules, and then return to that creative-point once the basic functioning of the game is well established and people can be comfortable with the idea of options that strike right to the core of the game's basic rules.
It's these relatively subtle nuances that distinguish the clones from each other. As playable systems, resources for one retro-clone are almost entirely usable with another clone rule-set. As approaches to the "feel" of a game, though, they are quite distinct and nuanced. For those who aren't stalwart aficionados of the old games, a discussion of retro-clones sounds as bizarre as a wine-tasting discussion (or beer, as the case might be :) ). And frankly, those distinctions aren't really important at that level of subtlety to almost anyone. The "old school" experience generally has to do with the open-endedness of the rules, and all of them have that common quality.