Today I was sending timeclock stuff via e-mail, and I had all my hours in a crazy complicated spreadsheet that took the raw data and made it pretty, collapsing the various sections of the day into one day, automatically discarding lunch and travel times - it was a pretty fancy Excel file. While I was typing, I noticed the relatively new Google Spreadsheets link in the upper-left corner of my screen, and decided to throw my spreadsheet at it. So I brought up Google Spreadsheets, after finding out that it did support a wide array of functions and fuddling around for a couple seconds, found the File button. So I hit File->Open, uploaded my spreadsheet, and after a bit (it's a relatively big file), checked it out. To my surprise, Google Spreadsheets handled it impressively, and everything was as it should be. That was very impressive - no complicated conversions, no fiddling, just open, and it works. Pretty sweet, especially for an online service.
The only minor drawback - I can't find a way to hide columns, which I want to do to get rid of all the intermediate calculations. But at first glance, GS is a powerful, well-built app. Dare I say, welcome to web 2.0?