It's open-source, cross-platform and very similar to µTorrent in both functionality and looks.
I think it is somewhat lighter resource-wise (I'm running it on my NAS), but apart from that I don't know the exact differences between Deluge and Transmission, but I thought I'd mention it for completeness' sake.
However, my experience is that some Qt apps on Windows behave normally, and depending on the application (but in this case, especially just the need to manage torrents) a web UI works just fine and avoids the waste of developer hours fighting against the local platform's quirks.
For my enlightenment, what do you consider as an example of a great Windows UI?
Deluge has all the features I want on a torrent client, I will replace my uTorrent installations on windows by deluge.