Honestly, I have yet to work with NMC on any projects although I have been in their system for well over a year now.
I am a bit put off by recent emails I received soliciting me for payment ("Sale ends at Midnight, total savings=$319!") in order to book work for me. I'm sorry -- but you make a commission off of my placements. This is really sleazy business tactic in my opinion.
I think the best agencies I've worked with are the ones that really try to take a unique approach with each talent that they represent and place. I understand it's a rapidly changing market and there needs to be a deep pool of talent to select from, but this just feels a little too impersonal.