I will do shops for Cirrus on occasion. However, the payments puts them pretty low on the priority list. Still, if I have a window of time during which I want to work and don't see other appealing jobs available, I'll do their work. I figure that money in four months is better than no money at all. In my area, other MSC's offer very similar shops to theirs - and generally for $5 or $10 more than what Cirrus offers. So, why would I take $35 in four months for a job when I can get $45 next month for the same job? The way I see it is: If they need/want to have the slow payment processing, that's their business. However, if they want me to pick up their jobs, they need to offset it with higher pay than the competition.
I actually sent a nice note to the scheduler about two months ago, outlining just this and offering to pick up some of their shops that had gone unclaimed for several months for the same price as another MSC. I got not response at all. About a week ago, half of their shops suddenly had their compensation bumped up to the level I had requested. I did as many as I could - but some simply went undone from what I can tell. The other half were changed to phone-only shops.
I don't mind working for them - they are nice enough folks. It's just that I can't justify taking their shops when I can fill my time with better offers from other companies.
Hard work builds character and homework is good for your soul.