I completely disagree.
MS is not a great negotiator, at all. Unless you think paying insane amount of money is being a good negotiator.
MS true strength is the fact that they can spend a lot of money to buy their way into some market. There is no negotiating in that.
I don't call paying $50 M to get exclusive GTA4 content, being good negotiator.
I don't call having to pay all the development for japanese games, being a good negotiator.
And I don't see a good negotiator home console maker losing $7 B dollars to this day on a console brand.
On the other hand, I always was amazed by how good negotiators 3rd parties (or even 1st parties) could be and scam MS into paying huge amount of money, far above the value of what they get in the end. That goes for Nintendo and Rare, Take Two and GTA4, Mistwalker and their JRPG, Namco for Trusty Bell, ...
Talking about goodies, I'm still always amazed by how blinded the MS followers are. That's something they are very good at too, blinding their followers. I'm thinking specifically of the Blue Dragon anime series. When it was announced and the first episode went to the XBL, I saw the first part of it, and thought : this is basically a crap anime, no one could ever call that enticing... to then hear the XBox followers call this anime very good... No need to say it had the life of a crappy anime series that it is. I don't know about the Viva Pinata cartoon, as I don't like cartoon, and couldn't give a good advice on it.
But that's just to say they throw money at anything, hoping for it to work. Sometimes it does, and that's their "strength".