When you create a new restore point with Checkpoint-Computer, you do not get back any feedback telling you whether the operation succeeded. Fortunately, you can easily lookup the corresponding event log entry:
PS> Get-EventLog -LogName application -InstanceId 8194 -Newest 1 | Select-Object * EventID : 8194 MachineName : TobiasAir1 Index : 15503 CategoryNumber : 0 EntryType : Information Message : Successfully created restore point (process = C:\Windows\system32\wbem\wmiprvse.exe; Description = Before script execution). Source : System Restore InstanceId : 8194 TimeGenerated : 28.05.2012 10:04:59 TimeWritten : 28.05.2012 10:04:59