@ikerrg, For random-access (including swap), class 2 or 4 is generally better than higher-rated cards (the rating is about continuous, sequential, writing). Many people around here (including me) have swap only on a uSD card with class 2 or 4 (I think mine is 2), and most (again, including me) find that responsiveness is generally better like that. But AFAIK no "true" experiment has been done. Nor needs to be done anyway. I guess no two N900s have the exact same settings anyway