I upgraded my server to Windows Server Essentials 2012 R2 (final from TechNet - not Preview) and successfully installed the .wssx version of the LO 2100 beta on the server.
I pushed the client install to all the clients.
It installs and runs correctly on a Win 8.1 client.
On Win 7 x64 clients, it appears to install, and the service is running, but the taskbar icon displays the 'service is not running' error.
The service log has an error:
2013-09-15 15:06:27:638 [ 1] INFO
2013-09-15 15:06:27:665 [ 1] INFO >ClientService ctor
2013-09-15 15:06:27:665 [ 1] INFO <ClientService ctor
2013-09-15 15:06:27:774 [ 4] DEBUG RequestAdditionalTime
2013-09-15 15:06:27:774 [ 4] DEBUG Initialized ResolveAssembliesFromProductDir, product dir C:\Windows\system32\Essentials
2013-09-15 15:06:27:774 [ 4] DEBUG ============================
2013-09-15 15:06:27:774 [ 4] DEBUG > OnStart
2013-09-15 15:06:27:884 [ 4] DEBUG ============================
2013-09-15 15:06:27:884 [ 4] DEBUG > ClientCore Ctor
2013-09-15 15:06:27:884 [ 4] DEBUG LightsOutClient Version : 1.5.4.2100
2013-09-15 15:06:27:884 [ 4] DEBUG .NET Framework Version : 4.0.30319.18052
2013-09-15 15:06:27:884 [ 4] DEBUG Running on machine/OS : P8Z77-V Windows 7 [Ultimate Service Pack 1], 6.1.7601.65536, CPU x64, OS x64, Program x64
2013-09-15 15:06:27:884 [ 4] DEBUG < ClientCore Ctor
2013-09-15 15:06:27:884 [ 4] DEBUG ============================
2013-09-15 15:06:27:916 [ 4] ERROR Exception OnStart System.IO.FileNotFoundException: Could not load file or assembly 'ProviderFramework, Version=6.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
File name: 'ProviderFramework, Version=6.1.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'
at LightsOutClientCore.ClientCore.OnStart()
at LightsOutClientService.ClientService.OnStart(String[] args)
WRN: Assembly binding logging is turned OFF.
To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1.
Note: There is some performance penalty associated with assembly bind failure logging.
To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].