Not exactly what you asked, but:
Chromakey is great for video because you always have software that does all the work, and since the image is rapidly changing, precision on each image isn't necessary. (but the cheap software still kinda makes crap results).
For still photography, my opinion is that an unlit white paper or light gray paper is superior to a chromakey. Green screen for photos is good for when you need to churn out a bunch of ok-quality photos with a very fast turnaround - for example, an event photobooth. But if you have high standards, the software to do it isn't going to be cheap.
With a green or blue screen, you have to be very careful with your lighting, and you have to have plenty of distance between the subject and the backdrop, in order to avoid a color cast from the lights bouncing off the backdrop onto the subject.
With a non-blown-out white or light-gray backdrop, you don't have to worry about such a color cast, AND, you might not even have to be super precise with your selections - just use a blend mode that works well around the hair and edges of your subject.