SQL Server 2008 R2 Nov CTP

I'm still debugging a script I have, but from what I can tell, I can't
simply do:
../setup.exe ... /SQLSVCACCOUNT="system" ...

I see this in the configurationfile.ini though:
SQLSVCACCOUNT="system"

I keep seeing an error in the summary.txt that the specified credentials
aren't correct, and I'm baffled at this point.

Because it is the system account, then I don't need to provide a password.

Is "system" in fact what I should use? Or should it be "local system" or
"nt authority\system"?

Marco