Is this diamond necklace worth it?

I think it's a decent price. The clarity isn't the best on the diamond, but it won't be as noticeable on such a small diamond unless the diamond ends up looking like frozen spit. Overstock is great about returns, so you could always order it and return it if it ends up not being what you expected.

Have you looked at the Blue Nile DBTY-style necklaces? There has been at least one reveal of it here that I can recall, and it looked really nice!