We have the IB program at my school, and there seems to be two opinions: people either hate it, or it's a necessary evil that is just there.
The people who seem to hate it are full IB (all classes except one are IB), because they see it as lots of work with no real gratification, and it has pretty much consumed their lives for the past two years. A couple of my best friends are full IB, and are absolutely sick of it. I only take four (English, History, Biology, and Calculus), but I understand what they are saying. You do a lot of work over a two year period, take the exams, and most colleges in the US do not know how to recognize them so a lot of schools do not give class credit for them. Also, you don't get your exam scores until after you have already entered college, so sometimes it seem pretty pointless.
I enjoy a few classes I take, and if you really enjoy a subject then it is worth taking the course in that class. If you enjoy the class as much as you think you do, then it is totally worth the time and effort, and usually your grades do not suffer. But don't just do it because it looks good on a college transcript -- I was pretty good at English and Biology and liked them well enough, but now I cannot wait until May to get out of those classes!
Rambling over.
Hope this helped a bit!