Technically it has no editions, just printings. Everything is backwards compatible. As importantly, converting AD&D 1-2e or D&D 3, 3.5, and 5e adventures are totally easy. If you have experience with any of those systems, C&C is about the easiest game out there to just pick up and start playing. Plus, the Troll Lords are great guys; veterans who keep all the political BS out of their games and make everything right here in the USA. Their customer service is fantastic. Their forums are also pretty good. Again, folks generally stick to talking about the game, not other stuff.
My only real criticisms are that their product editing is sub-standard and the quality of their published adventures is inconsistent. Some are good; a few are awful, and most are just okay. The editing issues remain there and I don't like their house style, mainly because they don't include full monster stat blocks. But I have a ton of old D&D material and write my own stuff so it doesn't matter much.
I will finish by saying that after being my intro to the OSR scene in 2016, C&C has remained my game of choice because for me it requires the fewest house rules with the most depth and options. It plays and feels like AD&D with modern mechanics and a unified system (the Siege Engine, based on attributes) that I prefer to what modern D&D offers. My players don't necessarily agree (they like OSE a bit more), but we play enough C&C and I highly recommend it if you're looking for an easy to learn D&D alternative.