The company hopes to generate a lot of positive buzz on message boards and demonstrate that the product's vaunted security functions can stand up to the scrutiny of hackers.
Longhorn will come loaded with Windows PowerShell, which helps simplify administration tasks via improved event logging, task scheduling and remote management.
It also includes improvements to Active Directory Federation Services, which makes it easier to implement new policies and make it easier to set up relationships with trusted partners.
The new server also features easier failover clustering, dynamic partitioning and auto-tuning networking features to help customers manage system resources and ensure that users have uninterrupted access to their company networks.
Customers also have the option to install Server Core, which helps reduce the server footprint and the potential attack surface of the network.
Virtualization, however, is one feature that Microsoft will not include with Longhorn when it ships, as reported by internetnews.com earlier this month.
Given the company's release schedule -- it plans to ship during the second half of the year -- the evaluation period is a chance for Microsoft to receive and react to feedback in time for the new product's release to manufacturing.
Bill Laing, general manager of the Windows Server Division at Microsoft, urged customers to take advantage of the testing period. "If there's one message we want to send today, it is get read, download and evaluate," he said in a statement.
Yankee Group analyst Laura DiDio said the beta period will be critical in determining the server's success.
"The first thing people start talking about [on message boards] is all the flaws... We should know within the next few days if there are any major flaws in Longhorn, how easy it is to use. Word of mouth is going to be very important," she said.
Microsoft has a lot riding on the success of Longhorn, as the Windows division represents 25 percent of the company's revenues, DiDio said.
In a sense, Microsoft may be a victim of its own success if Longhorn fails to take off as quickly as hoped.
Windows Server 2003 "is still a pretty good operating system, because Microsoft has been responding to customer demand for more security, more scalability, more granular management capabilities. Longhorn just takes it to the next level," DiDio
However, considering that Longhorn mostly offers incremental enhancements to Windows Server 2003, even customers who decide to upgrade may decide to wait 18 months or more, she said.