Thankfully, Metal Gear Solid: Peace Walker has an elegant solution for the former problem. Holding up on the PSP's d-pad will "sync" you with your sneaking partner(s) and, as long as the button remains held down, you'll stay in automatic lockstep with the leader. Remaining a cohesive group is an essential strategy for a silent approach, though splitting up offers its own advantages as well.
Peace Walker is at once a comforting, familiar experience and a surprising divergence from Metal Gear's longstanding methods. It's still a game of tranquilizer darts, cardboard boxes and rations, but the addition of local Wi-Fi co-op re-purposes each tried-and-true element for a brand new context. Knocking on a wall to lure in a dim-witted guard -- while your partner flanks him -- feels like an ideal mesh between the old and the new.
The same feeling applies to Peace Walker's controls, which wisely ditch the example set by Portable Ops in favor of Metal Gear Solid 4's shooter controls. Holding L will let you aim down the sights, while the four face buttons act as a second analog stick for aiming. As with every game in the franchise, there's a significant learning curve attached (the R-button serves three purposes!), but the camera sensitivity feels just about right. There's also an auto-aim option, though it comes at the sacrifice of more precise headshots. Failing that, there's also good ol' Close Quarters Combat -- tossing a foe to the ground now triggers a follow-up combo that also incapacitates a second or third in-range foe.
There's a good mixture of stealth and straight-up shootering in the Tokyo Game Show demo, with the start of each mission preceded by the selection of one of several suits. Snake can don a stealth suit, which gives him a silenced load-out and a useful shield for protecting fellow players, or some combat garb, which starts him out with decidedly unsubtle weapons like the RPG-7. Picking weapon sets that work well together is vital in the demos later stages -- like when it tasks you with taking out a platoon of soldiers and a tank.
There's only a brief glimpse of Peace Walker's plot within the demo (though even that comes in the form of several stylish 2D and 3D cutscenes), but the dialogue and overall presentation don't seem to have suffered at all in the shift to a portable platform. In fact, the game's codec sequences, which play without interrupting gameplay, are the least intrusive in the series ... ever.
One could also argue that Peace Walker could be the most innovative title in the series yet. It looks set to push Hideo Kojima's stealth stalwart into the realm of social play, without sacrificing the outstanding graphics and gameplay that Gear-heads have come to expect. Expect to see much more before Peace Walker's 2010 release.