Most of us knew that the first Matrix was pretty much a one movie deal. It didn't beg for a sequel, yet we got Reloaded anyways...and soon to come, Revolutions. So with Reloaded we get the whole Zion thing goin on (Zionists rejoice...tsk tsk tsk :-P) and the human element. What's wrong with Reloaded is: (1) Story, and (2) Character Development.
To explain number one, the story isn't all that well delivered to us. With the Zion environment, gone is the mystery and realism that made us, well at least me, love the first matrix so much. Not to say that it's all bad because I will go see Revolutions to see how it all ends, but for example, the big cliffhanger that's at the end, honestly it really isn't at all, because of problem #2. Number 2: Many more characters show up in Reloaded, like Persephone, the twins, a "new" agent smith(s), yet pretty much all these characters are so two dimensional. Their little screen time doesn't explain why they are there and why they are who they are, although the movie preaches "purpose." Unfortunately, it's hard to really connect with them and thus we have less feeling for what they do, and less feeling for the movie.
Another element that was pretty underwhelming was the music. There were no really good thumping songs that you could remember afterwords. In the first movie you had prodigy, propellorheads, rob zombie remix...in this one the only song i "got in to" was the freeway chase scene, which btw is the scene that, if anything for this movie, is worth your money.
So anyway, go watch it, because it is enjoyable - I was drinking a Lowenbrau maybe that helped too :-) - but just know that it's pretty average and it can't compare to the first movie...unless you're a graphics junkie/anime freak. Enjoy.