Ok, there isn't much that can be said about the American Pie movies that hasn't already been said. And that hasn't all ready been done.
There is something that feels natural about American Reunion though.
If we discount all the "American Pie Presents" direct to video releases, than American Reunion feels like the next, natural step.
Sure the 13th year reunion feels a bit forced and some of the stories lines feel a bit uneeded. But that is just how things go in the "Pie" universe. Regardless of what happens to Jim, we will always see him as the eternal virgin. Michelle the eternal band geek and all the other character will be their characters forever.
Stifler is the only character whose line I looked forward to what happened. I won't ruin it but he has a great cameo in his future.
All the story lines from Wedding, and even a bit from Pie 2 meet up in this film and I honestly feel is a great addition to the series.
At the very least American Reunion is better than American Wedding. It just feels more natural and has a more logical conclusion in the grand scheme of things.
After all that, all I can say is enjoy if for all its mindless joy :)