edit: I just noticed that you already know jinni. sorry.

I use jinni.com - it is basically last.fm for movies and tv shows. The site could need a better user interface, but the movies are very well tagged, which enables you to dig deep into niche categories. For example you are not only able to filter by genre (drama, comedy, etc.) which is very general, but instead there are filter options for the plot too (corruption, love, drugs, mind-bending,...).

Also their recommendation engine works quite well and gives you accurate suggestion which are not that obvious or popular.

So, while not cutting-edge, jinni.com is probably the closest to the movie discovery service i wish to exist.