We have it, and are currently playing through it.
It is OK. Mario Sunshine, Mario Kart, Metroid Prime, Windwaker, Pikmin2, etc. ....those games were really good.
But paper mario is only OK in my opinion. Some of the RPG battles seem so annoying, and like work. Some parts seem tedious, and not fun. But, overall, it was a pretty good game. Just OK, though...