Gamertell has posted a positive review of Atlus' Metal Slug XX for PSP.
From the review:
"Essentially, everything said in the DS review of Metal Slug 7 still rings true in Metal Slug XX. It's a wonderful action game that manages to be challenging and accessible at the same time. Newcomers and fans alike will be delighted by the clear graphics, battle school challenges, co-operative multiplayer and familiar Metal Slug fan."