The more I look at it (and the more I research them) the less I see this going anywhere. Yeah, they're not "officially" a vanity publisher, since they tend to be discerning (whereas vanity publishers are just out to make a quick buck with ANY work). But if they really believed my MG would do well on the market, they wouldn't be talking about "upfront payment".
Still, I'll look at the contract when they send it next week; I just won't hold my breath that it'll be any different than other people's experiences with them.
Guess I'll approach this with an "expect nothing, and you won't be disappointed" attitude. I'm better off focusing on FotS's launch, anyway. Still lots to do there.