For me, ATH is a perfect example of the old saying "Better the devil you know than the devil you don't know".
Yes, their payment terms are somewhat long, and it is a dirty (but legal) trick to slide the extra 10 days in there.
But, although it's slow, I've never been stiffed on a payment and a majority of their shops don't require a purchase. So while you are waiting for payment, at least you're not fronting money for 60+ days.
Plus, in my area, they have a ton of reoccurring shops which are, in my opinion, perfect filler/tack-on type jobs: usually between $10-12, no purchase, and high concentration of locations.
Also, they are usually pretty straight with me as to when they'll have bonuses available, as I tend to pick up 2 locations that it is all but impossible to get people to. They've also never unreasonably challenged any negative reports I've issued.
So, are they one of my "prime" MSC's? No, but they are generally one of the first I turn to if I'm in a lull or need some filler work to justify driving to an area.