Pros:
Promotional offers when you initially open the CC account (usually around $150)
Cash back (anywhere from 1-10%. A free 1-10% discount on everything you buy? Nobody would say no)
Build your credit (this could save thousands when you take out a mortgage)
Fraud protection (I know firsthand..if your CC info is stolen, you just tell the bank and you arent liable for ANY fraudulent charges)
Free insurance/protection (for car rentals and many others)
Travel features (easy foreign exchanges with decent rates, emergency assistance, etc)
Electronic purchase history (tracking expenses is incredibly difficult if it's all offline, aka cash)
Convenience (carrying cash is inconvenient, slower, and dirtier)

Cons:
If you don't practice self control you could get into severe debt.

Easy way to overcome the con: Pay off your credit cards weekly and budget/track your expenses.
Oh and your projections on cash back earned in a year are severely understated. But I think I've made my point.