The new application will focus on collaboration and sharing, allowing multiple people to edit the spreadsheet simultaneously. All users would see changes as they were made, with an area available to chat if needed. This is a list of main features announced for Google Spreadsheets :

Create basic spreadsheets from scratch. : You can start from scratch and do all the basics, including changing the number format, sorting by columns, and adding formulas.

Upload your spreadsheet files. : Upload spreadsheets or worksheets from CSV or XLS format - all your formulas and formatting will come across intact.

Familiar desktop feel makes editing a breeze. : Just click the toolbar buttons to bold, underline, change the font, change the cell background color, and more.

Choose who can access your spreadsheets. : Just enter the email addresses of the people you want to share a given document, and then send them a message.

Share documents instantly. : People with whom you share a given spreadsheet can access it as soon as they sign in.

Edit with others in real time. :Multiple people can edit or view your spreadsheet at the same time as you - their names will appear in an on-screen chat window.

Edit from anywhere. : There's nothing to download; you access your spreadsheets from any computer with an Internet connection and a supported browser.

Never lose your work. : Online storage and auto-save mean you need not fear hard drive failures and power outages.

Easily save and export copies. : You can save your spreadsheets to your own computer in CSV, XLS and HTML formats.

Currently the home page of the service spreadsheets.google.com returns an Error 404 Not found, but you can already check the SpreadSheet Help Center for more information about the service, how to use it, privacy and security... etc. Some of the missing features include graphs and macros which are planned for the future versions, support for IE6/FF1.07+ only available.

Now that Google has acquired Writely and released Spreadsheet, there is no doubt that they have plans to offer a complete web-based AJAX Office. Also the competition will be more difficult now that Google joined the currently established Spreadsheets businesses such as iRows, NumSum, ZohoSheet, JotSpot Tracker or wikiCalc... While rumors were all about an acquisition of one of those services, Google has preferred developing their own software now that they have the necessary tools and experience... or because the currently established web-spreadsheets aren't very advanced to provide the additional value that Google is looking for.

Update : Read also our review of Google Spreadsheet features on Googling Magazine