Answers

I agree that it really depends on what APs you are taking. Also, different APs are difficult for different people. I think statistically, AP US History is one of the toughest ones but that's also because it has the most test takers.

Honestly, I would go for it. The way I look at it is if you're going to be a senior (which I'm guessing is your situation), then you only have to work super hard in the first semester to get good grades to show the colleges you are applying to and it reflects really well on you that you're doing so many APs.
My friend said that APs also helped him save a bunch of time in college so it can either save you money by helping you graduate early or it can allow you to take more interesting elective classes so it's a win-win.

I'm taking AP Calc, AP Chem, AP Lit and AP art. I almost signed up for AP Spanish, but I love art and I figured I could just take the subject test in spanish. Still, everyone says it will kill me to take Calc and Chem together, but I am sort of excited. Taking such tough courses together will, I feel, better prepare you for a rigorous college semester, and it will impress colleges. Just be prepared to work hard!

YES! well.. at least for me it was. at the end of my sophmore year i was so hooked on going into as many AP classes as possible for junior year, just because it looked good. but dont be fooled by the two little letters "a" and "p." ofcourse colleges love to see that you took aps, or higher level classes...but it is so much better to do well in a normal level class or an honors class, than to torture yourself in APs, and only get "ok" grades. trust me on this one... it might not be worth it in the end.