Microsoft Lync Server 2010 provides complete presence, instant messaging, conferencing and enterprise voice capabilities through a single, easy-to-use interface that is consistent across PC, browser, and mobile device. You can Architect your deployment for high availability using data center resiliency and survivable branch appliances. Administrators benefit from a single, consistent management infrastructure, new capabilities to increase availability, and interoperability with existing systems. Administrators also use a new PowerShell-based foundation for administration consistent with Exchange Server, Active Directory, and other Microsoft server products.

Here is a high level overview of the new features/improvements in Lync 2010:

  • New User Interface
  • The "Me" Area
  • Contacts Enhancements
  • Privacy Features
  • Office and Windows 7 Integration
  • Application Sharing, Desktop Sharing, and Collaboration Features
  • Recording and Playback
  • Improved Meeting Join Experience
  • PSTN Dial-in and Dial-out Conferencing
  • Video Enhancements
  • Manager/Admin Enhancements
  • Call Park and Retrieve
  • Call Quality Checks and Diagnostics
  • Improved Audio Device Handling
  • Location and Emergency Services Support (E9-1-1)
  • Call Handling: Delegation and Response Group Enhancements
  • Enhanced Phone Experience

Here is a high level overview of the new features/improvements in Lync Server 2010: 

  • Operating System and Processor Support
  • Topology Changes
  • New Management and Administration Tools
  • New Presence Features
    • Enhanced privacy controls
    • Photographs in contact lists
    • Message waiting indicator for some phones running Microsoft Lync 2010 Phone Edition
  • New Conferencing Features
    • Single meeting client
    • New downloadable meeting client
    • Meet simple URL
    • New Conferencing Modes
    • New meeting admission policy and controls
    • Enhanced meeting access levels
    • Assigned Conference IDs
    • Presentation Mode
    • Controls to Toggle Entry and Exit Announcements
    • Lobby provides improved user join experience
    • Access to DTMF commands during call
    • Recorded name for anonymous callers
    • Simplified leader join
  • New Features for External User Access
    • Simplified installation
    • Streamlined management of Lync Server 2010 components
    • Consistent synchronization of internal and external Lync Server 2010 configuration changes
    • Improved security
  • New Enterprise Voice Features
  • New Monitoring Server Features
    • Richer Reporting including Dashboard View
    • Comprehensive Data for Usage Tracking and Voice Quality Diagnostics
    • New Management Features
  • New Archiving Server Features
    • Archiving of IM content and meeting content consolidated
    • Searchable transcript of archived information
    • Per-user settings honored for conferences
    • New policy settings

 

You can download the RC from here:
http://technet.microsoft.com/en-us/evalcenter/ff808407.aspx