Google Spreadsheets may not be as powerful as Excel, but there are some things that is much better for. Take for example our little intra-company predictions about the World Cup 2006.
Originally, Achilleas created an Excel spreadsheet with all the gamess, then we entered our predictions. The spreadsheet contains formulas that calculate almost everything, except the scores 
so all he has to do is update the sores after each game and we know who is ahead in our predictions, how many points each team has, etc.
Sharing the Excel spreadsheet was a bit problematic. We would have to use a shfile at the company file server, howevere we have to access to it from outside the company intranet. What’s more, we would have to make sure everyone has Excel installed and check how the spreatsheet formulas work with other simmilar apps like OpenOffice that some (including me) use.
Porting (= uploading and editing by hand some of the formulas) the spreadsheet to Google Spreadsheets turned out to be the (almost) ideal solution. Everything works more or less as if we were using Excel.
Pros:
- Only Achilleas can edit, all others are invited as “view only”
- Access from everywhere and any time -we just need a browser
- Real-time updating. Changes appear in (almost) real time to everyone browsing the sheet.
- It’s free!
Cons:
- Still beta, some problems appear (as expected), ex. importing XLS with merged cells
- Still beta, no real EULA between Google and the end-user, can’t be used for “real” applications if you do not know what may happen tomorrow…
- No graphs/charts (yet?)
- “Unable to display, more that 4 users viewing this spreadsheet at the same time” error (???)
Bottom-line: I am thrilled with it! It’s still early, but I am convinced more than ever that the Web is a great platform to develop apps -even those that seemed like a natural “desktop” creatures.