Update 10/6/10 - Added Lync schema version.

There are a couple of ways to verify if the OCS schema prep completed successfully.  The quickest way is to run the following LCSCmd after running the prep schema step:

LCSCmd.exe /forest /action:CheckSchemaPrepState

If the report shows everything as successful, you can feel confident that everything completed properly.  But, if you want to go that extra step, you can look in ADSIedit.

In ADSIedit, under the Schema Container, look for the ms-RTC-SIP-SchemaVersion.  Opening the properties, look for the "RangeUpper" attribute.  Check the list before for the correct value for your environment:

LCS 2005 - 1006
OCS 2007 R1 - 1007
OCS 2007 R2 - 1008
Lync Server 2010 - 1100

If you see the correct value for your environment, you can be sure that schema prep completed successfully.