I find that C&C tries to be too many things to too many people, and doesn't do any of those things well.
There are better takes on "rules-lighter" 3e. There are better takes on "revised AD&D."
Many find that it hits their "AD&D spot." It doesn't for me, at all. It scraps all the little fiddly bits that were AD&D to me and replaces it with the SIEGE system. Maybe it's a 1e-2e thing. It feels a lot like 2e to me, completely vanilla, which is simply not what I'm looking for in AD&D. If I need an in-print AD&D, OSRIC or Labyrinth Lord with the AEC are both better bets.
It's not particularly rules light. Maybe by comparison to 3e it is. But by comparison to pretty much anything else, it's not. If I want rules light, I'll play Basic D&D. If I want rules light with a unified mechanic, I think both Tunnels & Trolls and the new Dragon Age RPG are superior games.
Of the half-dozen or so C&C adventures I have, I have found them to be between average and horrendous in quality. The cartography, in particular, is quite poor with keys and scale often missing and multiple occasions where the description in the text fails to match the map. In one adventure, U3 Verdant Rage, they forgot to include a map. They made it available as a download, but still it shows the lack of concern they seem to have for what I consider to be the single most important aspect of an adventure.
Of the C&C products I own, I find the original "Nostalgia" boxed set that came out back in 2004 or so to be by far their best product. If I were to recommend a C&C product to anyone, that would be it. Also, Gabor "Melan" Lux has made at least three fine free C&C adventures that I'd recommend people track down.
I agree C&C is Vanilla, but the other reason I remain a fan is because I found it easy to spice up to be precisely what I like, once I became a fan of the SIEGE engine, which did take me some time. Like I didn't get rid of my skill system I mention back in the 2008 posts in this thread until last year, now I just use the pure SIEGE engine. Lots of people like granularity, I like simple and gets the job done, and for me the SIEGE engine does that better than any mechanic I am aware of.
So if you don't like house ruling, and want a system pretty much ready to go as is, I doubt C&C and its SIEGE engine will be liked.
See, to me, C&C is a lot like a cake. C&C is the basic cake mix, and then it was up to me to decorate it until I was perfectly happy with how it looks. It took me a while, in fact it took me several years to get to where I am now with it, but it paid of in giving me absolutely the best RPG cake I could ask for.
So C&C is definitely not for everyone. For a good while I doubted it was for me. Now I am darn glad I stuck with it because I could not ask for a better D&D style RPG. It gives me everything I want, largely because I added a lot of what I want.
I mean, look at my house rules, I certainly do not run it by the book. It is MY C&C, not TLG's C&C. Which is why I love it so much.
I agree their modules are very hit and miss. One module in particular really irritated me, but I fixed the problems, ran it, and we had a lot of fun. One thing I have found consistently weird, the modules I had to "fix" are the ones my players most frequently comment on as being among their favorite "events", and the events they refer to were the ones in the modules, not one of my fixes. So I guess its like finding a diamond within a lump of coal. I haven't ran into the map/description compatibility much, but I did in that module that ticked me off. Still glad I ran it, though.