How To Use Web Apps to Create New Document
At first glance, the Office Web Apps seem surprisingly complete. As long as you are "just checking the numbers" that your office prepared while you are traveling, the currently available versions of Office Web apps will serve you just fine. Likewise, small edits to the text of a document, or even typing in a standard letter or memo are all handled smoothly and cleanly by Web Apps.

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Even more impressive is the interface of these online Office applications. When you first start up Microsoft Excel Web App, for example, it looks virtually identical to the default installation of the desktop version of Excel 2010. Indeed, for basic Office document editing, creating, and collaboration, Microsoft has hit a homerun with the Office 2010 Web Apps.
That being said, if you are a power user of Office applications, you will want to stick with the desktop versions for now. While it would be unfair to expect that every single possible formula available in the desktop install of Excel 2010, for example, be available in the online version, there some missing pieces that can limit the usage of the online versions for advanced users.
The Office 2010 Web Apps are still in beta, although anyone with a Windows Live account can sign up. Getting an account is easy. Check here for how to get a Windows Live account. Using web apps is not intuitive unless you plan to create your documents on your desktop first, and then upload them to your SkyDrive before using web apps.
To create a new Office document with Web Apps, you first have to login to your Windows Live account (home.live.com) then navigate to your SkyDrive (it's under More). Once there, you'll need to go into one of your folders whether shared or not. Then, look for the "New" along the menu row. From there you can create a brand new Office document with Web Apps 2010 from scratch.
Oh, there is one more catch. Currently the only documents that can be created on Web Apps are Powerpoint presentations and Excel spreadsheets. The menu options for Word and OneNote are there, but clicking them reveals a "We're Working On It," webpage.
In all, the Office 2010 Web Apps show a TON of potential. Unfortunately, Microsoft has been coy about just how complete the Web Apps will be when Office 2010 ships this summer. Just how far along they are may determine whether or not Web Apps becomes the killer app for MS Office 2010, or if they are just another add-on that nobody really uses very much.