Since we are on the topic of the contrary opinions, here is another one:

Anime I'm glad I didn't drop

Mai-HiME is the single best example of "you never really know." The first half featured vapid and seemingly worthless school hijinks. But this was all a (admittedly poorly executed) setup for an absolutely phenomenal second half. The anime went from "bottom rung" to "top tier" in a single scene at the drop of a brilliant plot twist.

When I dropped Mai-HiME, I knew where the second half was going, and I did not like it one bit. Just like Xenoglossia, actually.

By the way, do you know what makes it hardest to drop? Having bought half of the DVDs. Ergo: never buy unwatched.