The first year I started shopping, IntelliShop was one of my favorite MSCs. They had a lot of shops in my area and offered decent pay on some, and willingly bonused the not so decent pay ones. I didn't have pay issues or editing issues. My shops were consistently rated at 9 and 10.
Lately I shop for them less and less because I am disgusted by the sub-par pay rates. Even after bonuses some of these rates are still too low for the effort required.
It's been well over 9 months since I have taken any shop with this company.
I have not had the situation described by the OP happen to me with any MSC. I don't buy the date conflict excuse. I think they found a cheaper shopper and played dirty. Hearing about this, the severely delayed editing on some car shops that happened awhile back, and continuing to see their insultingly low fees in my inbox every day makes it less and less likely I will be shopping for them again.
I hear a lot of shoppers complain about multiple MSCs that treat their shoppers like dirt, but in my opinion IntelliShop is the only MSC who I would say truly does undervalue their shopper force and behaves as such.