I have not played Swords & Wizardry rules, but it is close to original D&D and has a lot of support and interest in the OSR community.
I have collected the free rules, core, white box, and complete, and today, I bit the bullet and ordered the hardback S&W Complete and the GM Screen. There are also a lot of cool and free resources in modules and other game supplements. They all have ideas that help inform me as a DM and a player.
Swords & Wizardry is often the go to ruleset for online contests among the OSR.
One big benefit of these rules, is that +Matt Finch has allowed others to hack them to suit their needs, and there has been a plethora of rules for many genres, including other fantasy variants.
There are also many games of other genres that use S&W rules. Just today, two science fiction genre games were announced, and both sound cool. White Star by +James Spahn and Outer Space Raiders by +Chuck Thorin. Each had their own take on the genre, and since both are based on S&W, I can see taking bits from both.
There are many other articles with ideas for in game, and on the experience others have had in play with Swords & Wizardry.
Catch the Drink Spin Run livecast tonight.
There is a G+ page for Swords & Wizardry, where you can catch what others are doing with it, either play reports, new supplements, etc.
Swords & Wizardry also has its own SRD: Official Swords & Wizardry SRD
Get the three different rule set here: