Michael, ive got the 35mm f2 (only just bought 2nd hand so not used loads yet), 50mm 1.8, 60mm 2.8.
Since getting the 60mm i havent used the 50mm. I guess it depends on whether your also interested in Macro? I like having the option to experiment and try macro stuff too, though i would recommend a flash for this as the DOF can be paper thin.
I have an 18 month old and i prefer the 60mm for portraits of her. It can sometimes hunt a little in low light - i dont know whether being a macro lens makes any difference there ?
On the whole though its very sharp and i would definetly recommend (i read loads of reviews and it was always rated as on of the sharpest, especially for EF-S).
I like tightly cropped pics so i use this more than the 35mm, the 35mm is there more for when i need wider.
Hope that helps in some way
Also, i did try the 50mm Sigma but my camera cant microadjust, and both copies i had severaly back focused. Looking at sample reviews, if you can persevere with sending lens back and forth and can find a good sharp copy of a sigma they are impressive. I have a couple of shots from teh Sigma that i kept from manual focussing (very hard with a toddler!!) and the bokeh is more pleaseing than the 35/50/60mm in my opinion.
Heres a sample, close up, from the 60mm, though i will add thats using a flashgun too which on first impressions i would def recommend for indoor/low light/freezing little monkeys!
Chocolate Mousse Warpaint by
Bluem00ner, on Flickr