I'd heard of Technorati but never looked into it as a very small scale blogger with no plans of either world domination / huge amounts of advertising dollars and therefore haven't worried about low site traffic.
Again, the tagging does make for an easy browsing experience. It relies on the honor system (as does much of Web 2.0) in that people who tag tend to tag correctly (not adding "shoes" as a tag to a post about suitcases, for example). There's always going to be hit and miss with people seeing their tags as applicable when other people don't.
Nothing seems surprising in the popular searches - both Britney Spears and Christmas are in the top 15. I'm happy to spot multiple word tags (whoo!).