Metal Gear Solid Portable Ops + review at 1up.

"Less of a sequel and more of a stand-alone expansion pack to the previous excellent PSP offering Portable Ops, Plus delivers another compelling dose of Metal Gear Solid stealth-action gameplay in an easily digestible, bite-sized form. The $20 price tag should clue you in that it's not the meatiest of offerings, but Portable Ops vets won't be disappointed (in fact, importing your characters from that game gives you a keen advantage here), and newbies may even find this psuedosequel to be an even more accessible entry point into the fun, addictive world of multiplayer online MGS."

Full Source: 1up