It’s for costing you a whole lot more money than Open Office’s Calc.
But, as far as spreadsheets, I use them all the time. They track labor, inventory, I do productivity and cost breakdowns.
I often make up a new spreadsheet to take care of calculations that otherwise would require to tallying up things on a calculator or something. if I’m going to have to type it into a calculator once, I may as well type it into a spreadsheet, that way I can tell if and where i’ve made any errors, and use that data in other ways if I want to.