BEFORE (OCS 2007 R2)
With Lync Server 2010 this setting is now only accessible through PowerShell. To view the media configuration for Lync, run "Get-CsMediaConfiguration".
AFTER (Lync Server 2010)
You'll notice from the above screenshot that mine is set to use HD video; the default in Lync Server 2010 is VGA quality. To change this, use the "Set-CsMediaConfiguration -Identity Global -MaxVideoRateAllowed Hd720p15M". Possible options are Hd720p15M, VGA600K, and CIF250K.
You can also create new media configurations on a per site or per service. For example, "New-CsMediaConfiguration -Identity Site:Edmonton -EnableQoS:$True".
Just remember that you need two quad core PC's to do HD video! For a complete list of requirements, visit: http://technet.microsoft.com/en-us/ff536101.aspx