I've been watching dramas for 10+ years and this is one of the funniest I've ever seen.  It's got everything: plotting and scheming ajummas, gangsters, cute kids, spies, and the perfect robot mother.  She's an unforgettable heroine, never letting her enemies tear her down and solving problems with 100% efficiency.  The lead actress does a great job of making her both innocent and single-minded in her determination to do the right thing.

My one caveat is that to get some of the jokes you need to know a little about Korean culture, so it helps if you've already seen a lot of dramas before this one.