I ordered a total of 7 chickens from MPC. There was an original batch of 6 bantams- 4 silkies, 1 EE bantam, and a buff brahma bantam. 2 (the brahma and one of the silkies) died w/in 24 hours, and didn't look so hot when they arrived. I got excellent customer service on the matter, and opted for 3 Wellies as replacement birds. All birds were sexed. So far, I've been quite happy with the surviving birds, and nobody seems to be in danger of dying (although, you just never know). The birds are 5 weeks old on the bantams, 4 on the Wellies. I am beginning to get a little suspicious that one of the silkies is a roo, though. Obviously, it's too early to know for sure, so I'll just have to wait and see.
I would say that, overall, I have been quite pleased with the service I've gotten from MPC. If it turns out that I have a roo or two, I'm fairly confident that they will take care of me on it. It would be even better if it turned out that I have all pullets, but I'm not worried about the investment I made for the sexing. MPC has so far proven themselves to be good as their word on making things right, so one way or another it will work out.