ha ha! I haven't heard Service Sloth before... that's a good one.
I agree that they're one of the slowest paying MSCs I work with. I've been consistently doing shops with them for about six months or so, though, and I've never had to chase payment. My notes say I've been paid on the 30th, 28th, 23rd, .... usually right before the end of the month by Paypal. Feb 2nd doesn't seem unreasonable since the last day of January is a Sunday.
I try not to do too many shops for them since they're on the slow side in terms of payment speed. Unfortunately (or fortunately) I really like a few of their shops, so I find myself going back despite the slow payment. If I had to chase them down for payment, that would be a different story, but it hasn't happened to me yet.
Shopper in California's Bay Area