You receive platinum status after you have 75 nights in a given year (or rolled over, or from MR Visa credit card use). Platinum Premier is a whole different thing. There have been numerous discussions about this, so I'd suggest doing a site search for "platinum premier." ProfChiara
I think the answer is the world or not much. For me, the premier line is always amazing to work with and I'm rarely, if ever in queue. That said the platinum line was pretty amazing in their own right, I never really ask them to do too much heavy lifting as it were so maybe its just the higher level of service perceived on my end? The real bonus is the one little box that says "upgraded to a great room if available" (paraphrasing of course). In most hotels that have variations in room type, I have found being a P.Premier has almost always provided some level of upgrade, often to a room type that I find myself amazed by at times. At resorts and full service hotels I've found that these upgrades can also extend to a variety of other perks that vary by property. If you are a loyal MR member that frequents Springhills, Fairfield, Residence Inn or perhaps even Courtyard properties these types of upgrades really do not exist so its harder to realize the added value. Even at these properties I'm given something, even as small as arrival bonus points AND a snack or double arrival bonus points. There are a few exceptions but I've noticed a great deal more "perks" after having achieved Premier than when I was a Platinum, Gold or Silver.....and with the requirements for getting Premier I think its worth the added goodies :) I will say that of all the hotel loyalty programs, in my opinion the MR program rewards its most loyal members incredibly well.