Take your top 50 artists. For each of these artists, collect the top 20 similar artists (where the artist itself is the #1 most similar). The resulting number of unique artists is your super-eclectic score. You can compute your own score.According to the test website: "People with scores over 700 have bragging rights. People whose score is below 400 should consider more musical styles!"
My super-eclectic score is currently 703/1000.
The most similar artists for my profile are 桜庭統 (8), Stephen Schwartz (7), Company (6), Hootie & the Blowfish (6), 崎元仁 (6), 植松伸夫 (5), Original Broadway Cast (5), Masaharu Iwata (5), 光田康典 (5), Andrew Lloyd Webber (5)
I'm not sure how accurate the test is since I've been on last.fm for less than a month. I tend to listen to the same music for a long time, then move on to another artist and listen to that person for a long time, etc...