With Microsoft Office 365, Microsoft finally has a formidable entry into the office web application space. However, unlike its main competitor, Google Docs, there's no free version of Office 365. There are two basic editions of Office 365: Office 365 Plan P for professionals and small business, which is limited to 50 users, and Office 365 Plan E for enterprises. Plan P is available for a subscription fee of $6 per user per month; Plan E is available in four different levels ranging from $10 to $27 per user per month. Let's take a look at some of the most important features in Microsoft's cloud-based Office 365 offering.

10. Browser-based access—You access Office 365 by pointing your web browser to the Microsoft Office 365 portal. Office 365 is compatible with all the major browsers, including Microsoft Internet Explorer (IE), Firefox, and Safari. Notably, Office 365 can be used from either a Mac or a PC.

9. High availability—Falling on the heels of recent outages from both Amazon and Microsoft's predecessor online service (Business Productivity Online Standard Suite—BPOS), you have to wonder how this claim will actually pan out. However, Microsoft is providing a 99.9 percent uptime guarantee for Office 365 and offering refunds for any outages.

8. Lync 2010—Office 365 prompts you to download and install the new Lync 2010 client. Like Windows Live Messenger, Lync 2010 is an IM client that lets you conduct online meetings. Lync 2010 provides PC-to-PC audio and video connections. Unlike the other web-based members of the Office 365 suite, Lync 2010 is installed to your desktop.

7. Web design app—Office 365 includes an easy-to-use—albeit limited—web page designer. You start the web design app from the built-in SharePoint site, and it provides a set of templates that let you quickly create and edit very simple websites. The web design app isn't nearly as rich in functionality as the other Office 365 web apps.

6. PowerPoint Web App—Office 365 includes web versions of the main Microsoft Office applications, as well as the desktop Office suite applications at higher subscription levels. The PowerPoint Web App can create new presentations or open existing documents. I was pleasantly surprised at how similar the Web Apps are to their familiar counterparts in the desktop Office suite. I was immediately productive with Office 365 Web Apps.

5. OneNote Web App—Like its desktop counterpart, OneNote Web App is a note-taking application that doesn't require you to explicitly save your documents. The Web App is simpler than the desktop version of OneNote in that it doesn't have multiple tabs across the top. However, you can sync your desktop OneNote with the web version.

4. Outlook Web App—Outlook Web App (OWA) is the browser-based email client. Office 365 OWA uses Exchange Online running on Exchange Server 2010 as its mail host and provides the same left pane navigation, reading pane, and calendar functions that Outlook users have come to know and love. Each user gets 25GB of email storage.

3. Word Web App—Arguably one of the foundation pieces to the Office 365 suite, the Word Web App can be used to edit documents. It includes all the basic word processing features, such as formatting, word wrap, and spell checking. As a heavy Word user, I was pleasantly surprised with how fast and useable the Word Web App is. Like their desktop counterparts, all the Office web apps feature the Ribbon UI.

2 .Excel Web App—
The cornerstone of the Office 365 suite, the Excel Web App lets you create and edit Excel workbooks. It works much like the desktop Excel client and provides support for basic Excel functions and formulas. It also supports multiple users simultaneously editing the same worksheets.

1. Team Sites—One of the core features of Office 365 that makes it really useful is the built-in SharePoint site. Office 365's Team Sites feature is actually a hosted SharePoint Online site that both enables online storage for Office 365 documents and allows multiple users to collaborate on those online documents. The SharePoint back end provides the backdrop that makes the components of the Office 365 suite really useable and sets the Office 365 offering apart from competitors such as Google Docs.