Brian, I'd say that if you're up for the workload then go for it. Keep in mind that it was harder than ever to get into college last year and its going to be harder for your class (so they say). My major concern would be that this class hurts your performance in other classes. Senior year AP history is supposedly the hardest class you can take in HS, my friends who took it had to go to study sessions after school and on the weekends, buy hundreds of dollars in prep materials for the AP test, etc. etc. Its a ton of work and a big commitment so I'd just be concerned that you put so much work into that class that it hurts you in other classes (especially if you're taking multiple AP classes) and then you end up at the end of the year with lower-than-expected grades in your other classes and still a C in AP history.
Also a random note; don't be too concerned with college. Just do your best and try to have some fun every now and then. Its pathetic seeing how many kids in high school who basically set their sights on Stanford or Berkeley or somewhere like that and when they don't get in they're devastated and bitter. There's a TON of great colleges out there, a lot of elite colleges you've never even heard of. After your first job in the real world no one gives a shit where you want to college. In short, just be open and positive becuase its going to be nuts trying to get into any reputable college for you. College will be what you make of it- its nice to get into the big name schools but don't be discouraged if you don't get into your top choice.
I still remember my first class of high school with my honors (and later AP) english teacher who's ancient and been teaching for like 50 years. He started off by saying "anyone have dreams of going to stanford or princeton? Forget it. You're not getting in." and he went on to say some of the things I just said. He was pretty much right too and I went to a rich bitch private HS with crazily smart and dedicated kids.