I had heard about this anime, but I only started watching it a couple weeks ago when they started showing it on Adult Swim on Cartoon Network.
After only the first show, I was hooked on it, and I think it's for much the same reason as why Clue is my favorite movie. It's funny, and suspenseful (well, at least the superb episodes are), and thought-provoking all at the same time, and it gives the viewer ample time to think through the case right along with Shinichi.
At first, I couldn't understand why they put it on Adult Swim instead of Toonami, but after watching some of the episodes, I saw the reason... even though it feels like a kids' show, a lot of the cases are murders, and they sometimes deal with heavy topics (like losing a child)
If you enjoy mysteries (and even if you don't, this might get you into them :P ), I highly recommend watching this show. You won't be disappointed!