As noted earlier, W&W has been refined and renamed to "Misfits & Mayhem," as well as broadened from just 4E to include late 3E and even some forms of 2E. It's still similar to P&P, but characters tend to be more varied and a bit less clean-cut, tending to get themselves into trouble as much as they help out others. It's also a more high-action game, and a bit more cynical and 'shades of gray'.
As Kai Tave put it on the RPG.net thread, "if P&P is the Jedi Knight then M&M is the smuggler with the beat-up spaceship and the weird alien co-pilot. They're similar enough that they can team up and have adventures together but distinct enough to each have their own flavor. "