Oh indeed... It's strange really, considering a large part of the staff is more or less raving yaoi fans...
My favourite yaoi mangaka is probably Yamane Ayano... I love her art (and I've got a weakness for long-haired bishies such as Feilon from Viewfinder and Havi from Crimson spell). I'm obsessed with Viewfinder. Storywise, though I could probably find other yaoi manga with a bit deeper storylines. But I need to satisfy my desire for good art too... and smut... lots of smut
I do also enjoy Chi-ran (some of her(?) storylines are so wonderfully dark and twisted... like Install, yum!), some of Masara Minase's works and of course Tohjoh Asami (why oh why did she have to die?). As you might notice from this list I fall for those with clean art and bishies. If they know how to draw good eyes on their characters it's a sure-fire way to get me hooked.
My dream would be if Yoshihara Yuki created a yaoi manga. That'd be somewhere along the lines of the eight wonder of the world in my book.
Which are your favourites?