Pros:  Lightweight. Simple. Works on multiple windows systems. Calculates percentages in simple terms: "(amount) is what percent of (amount)?" "What is (amount) % of (amount)?" "(amount) is (amount) % of what?"

Cons:  Doesn't figure out how much a bill will be after tax: (amount) with (amount)% sales tax is a total of" I guess you can't have everything for 68kb :)

Other Thoughts:  Wish I would have stumbled across this years ago. Probably wouldn't have as much gray hair.