A few days ago, I ran the second session of a new campaign, which takes place in an original setting I call "The Sundered Land." I used Basic/Expert D&D rules with a mixture of Lamentations of the Flame Princess for our first session, but for the second session I switched to Swords & Wizardry White Box. Thankfully, my players didn't protest, and except for a few hiccups, it went smoothly. I really like the unified saving throw. It reduces unnecessary complexity, and enables a game designer to customize it as simply as adding a saving throw modifier. I like ascending armor class much more than I ever thought I would when something like it was introduced in 3e, and at least one of my players was overjoyed when I announced the change. (I should mention here that I have five players in this campaign. Two had never played a role-playing game before, two had never played an Old School game before, and one thinks she might have played 1e or 2e a long time ago, but isn't sure.) Anything that simplifies the process is good for both me and the players, as I think none of us like to get bogged down in details that distract us from the adventure at hand.
For a 1st edition AD&D and Basic/Expert D&D gamer, it was a revelation how better suited to my gaming style the Original Game and S&W White Box are. I like the absence of weapon proficiencies. That is a level of detail I never needed in my fantasy adventure game. There are no alignment languages, which is nice and sane. I like the unified weapon damage, as it requires no consultation of the rules and encourages weapon choice based on how players envision their characters. I like the unified hit dice system, as it reduces power inflation amongst player characters and monsters. I like the reduced attribute bonus range for the same reason. Most of all, I like the overall simplicity of the game and the vast blank space where I can create whatever I desire without bumping against another rule. That is what makes the Original Game so powerful. Swords & Wizardry White Box just executes it more elegantly. This is my edition of choice.