This is easily the most forgettable entry in the Mario & Luigi series. The story is flat (no pun intended), the "big paper" battles are just alright and the music is just alright. Additionally, having Paper Mario on your team and 3 moves per turn makes you feel overpowered too easily. Finally, the final boss is the most predictable and uninspired finale to a M&L game for me.
Having said all that, it's still a M&L, which is a very fun playthrough at the very least.