I don't know if you still care a month later, but since I'm here I might as well answer.
My first novel was published by MNW last November. Sales have been good, and now that it's out in paperback it seems to really be moving. Before the first novel came out I wrote a second, which resulted in a further two-book deal with Macmillan (not MNW). The second contract was much better, and all clauses fully negotiable.
I will say the standard MNW contract, which is not negotiable, is not ideal. But their books look great, are stocked as you would expect books from a major imprint to be stocked ... and sell like first novels sell, which is to say unpredictably. The ones that manage to gather momentum, for whatever reason, move while the ones that don't, don't.
But their in-house publicists work their asses off (I was reviewed everywhere, wrote several short pieces for magazines and newspapers, did interviews), their rights guys work equally as hard (sold US rights to Penguin, and so far have also sold German, French, Spanish and Dutch rights ... and maybe one or two more), and their editor knows what he's doing.
The real question is, can you swallow that first contract. For me, it was worth it. My second book came out in July, my third is being copyedited as I type this, and I haven't had to do anything for money this year but write.
I will say, though, that a few lucky breaks contributed to this.
In any case, no matter what you decide, best of luck in placing your work!