I've been playing a lot of Peace Walker, and I'm liking it. I've got the plot all reconciled with the greater continuity now: after the events of Portable Ops, Big Boss joined the Patriots, was unwittingly cloned in the Les Enfants Terribles project, and fell out with Zero, Para-Medic, and Sigint over the interpretation of The Boss's will. Big Boss left the cabal, with Eva and Ocelot also breaking off and going their own ways. It was from there that he went on to found Militaires Sans Frontiers, meeting McDonnell "Master" Miller, and establishing a presence at a ramshackle base on the Colombian coast before being approached (at the beginning of Peace Walker) with the proposition of ousting a foreign army from Costa Rica in exchange for a newer, more permanent base for MSF, and one in international waters--the perfect placefor Big Boss's vision of a nation for soldiers that are for hire to any government but beholden to none, a vision he calls "Outer Heaven."
I'm pretty comfortable with the controls now, and I'm settling in for a long ride through the game. It takes a lot to build a nation based on the war economy. I've made it past the third major boss encounter, a battle versus an "AI Weapon" called Pupa. These battles are the best analog to a Monster Hunt in the game, and indeed I even played it once in co-op, using the PS3's adhoc party app to find another person out there in Internet land playing the game. It was pretty cool, though it's a lot of hoops to jump through for the experience. I later went back and replayed the encounter solo just to see if I could pull it off, and I did without much difficulty. The incentive for replaying like so is basically to get better drops (AI Weapon parts), and to use those to build the MSF's own bepedal nuclear tank, Metal Gear ZEKE. Once operational, ZEKE will be MSF's own nuclear deterrent, protecting the fledgling nation from outside aggression via Mutually Assured Destruction.
So, aside from the dubious choice of platform, I'm pretty happy with Metal Gear Solid: Peace Walker. It seems Kojima has actually decided to put it in the series' chronology in an epoch that both makes sense and needed a little elucidation. I'm nowhere near done yet, though, so we'll see how it goes from here.