Just a bit of background on my history with D&D. I never really got to play basic D&D back in the day (though I really wanted to). I eventually did buy the Rules Cyclopedia when it came out, but never really got to use it for anything. When I went off to college, AD&D 2nd edition was the game of choice, so that's what most of my experience is with. I've also played around a bit with 3.5 D&D, mostly with video games. Having said all of that, I haven't actually played an actual D&D gaming session in years.
A bunch of my colleagues at work told me they wanted to play D&D, so I figured why not play RC era basic D&D. After just getting things off the ground running B1-9, I got curious hearing about all of the OSR retro-clones. Labyrinth Lord was a name that kept popping up continually and it referenced the B/X or Moldvay ruleset which I had never heard of until now. I figured how much different could it really be from the RC? It's different all right, in a really awesome way. Comparing this system side by side with the RC, I feel it is much better balanced in every way. I know B/X capped out at level 14 and this one goes up to 20, but everything is still pretty close to that version of D&D. It's definitely an easy pick up and go system, and I appreciate the simplicity.
You may be asking, why would I recommend Labyrinth Lord over B/X then? Two very big reasons. First of all, you have everything you need in one book rather than two. That's something the RC always had over every other version of D&D before and since. The second reason is that this system can be expanded with the Advanced Edition Companion if you want some more character options, but not so much as to slow things down where it takes a full day to make a character. If you just want the standard B/X playstyle, then this book alone is all you need and it works really well. There's also an expansion for people who want a game more like OD&D, but I can't say anything about that one as I know nothing about it or OD&D at all. I guess there is a third reason to get it. There are a TON of supporting materials by third-party publishers on this site if you just search for Labyrinth Lord under rule system. With all of that material, you can really make this game into just about anything you want. I'm personally just sticking to this and the AEC and I like what we have going. You can always read through the no-art version for free, but I prefer having art and at this price, you can't really beat that deal.