Thanks for all the replies! Unfortunately the sigma doesn't fit into the budget.
I do shoot kids sometimes, as I work at a day-care center, and would love to get some "fast 85" pictures of them as well. All that aside, my primary purpose for this lens would be portraits of my soon-to-be-wife (for her fashion blog) and friends in controlled out-door environments (well, as controlled as out-door environments come). For this purpose, i believe the samyang would do a better job, as I would probably use manual focus (using live view) anyway.
But, (there's always a but) I love to take my 50mm 1.4 out with me when i'm just taking a longer walk with the dog and stuff, I would also love to do this with my 85. I have my dog on one hand and the camera on the other, so i usually have my camera on Av mode, center af point selected, and then I just point and shoot to anything. Couldn't do this with the samyang. And also, i love the laughter and smiles of kids parents when I show them the pictures printed from the 50mm 1.4, with samyang shooting kids would be more difficult. (not impossible, just more difficult.)
So difficult to decide! Does anyone have a link to a side-by-side model shoot to clearly show the differences of these lenses?