I had several friends in IB. They are now seniors in college. They said it wasn't really worth it and they're no better off than the other smart kids at my high school.
IB isn't any harder than taking a full load of AP classes. Also, IB focuses more on history, writing, etc. If you want to go math/science route, you're better off taking all of the AP classes for biology, chem, physics, math, computer science, etc.
That being said, I went to a good high school (it was the academic magnet). We had very good teachers for the AP classes. Our classes were significantly harder than the other high schools in the city. IB might be a better option if your high school doesn't offer good AP classes.