Beautifully written. However, there was one or two chapters in the middle that devote themselves to talking about Dorian's various fads and passing interests, and while I enjoyed the flowery prose they just meandered uninterestingly and I didn't see how they added to the plot or to the allegory—although it's very likely that I could've just missed the meaning. Other than that though, I really enjoyed it. Wonderful philosophical introspections (including questionable ones by Lord Henry), and a consistent but hidden underlying allegory (although admittedly obvious if you know about Wilde's personal life).
Unrelated, but even if I didn't know Wilde was primarily a playwright I still would've been able to tell because all the dialogue feels like a play rather than a novel.