SQL Server 2008 R2 unattended installation via configuration file

I wrote about unattened install of SQL Server 2008 R2 here, where all parameters were entered on the command line directly.

Another way, perhaps a better way, of automation is to put all parameters in a configuration file. Here is a sample:

[SQLSERVER2008]
; Specifies a Setup work flow, like INSTALL, UNINSTALL, or UPGRADE. This is a required parameter. 
ACTION="Install"
; Specifies features to install, uninstall, or upgrade. The list of top-level features include SQL, AS, RS, IS, and Tools. The SQL feature will install the database engine, replication, and full-text. The Tools feature will install Management Tools, Books online, Business Intelligence Development Studio, and other shared components. 

FEATURES=SQL,Tools
INSTANCENAME=MSSQLSERVER 
SQLSVCACCOUNT="NT AUTHORITY\SYSTEM"
SQLSYSADMINACCOUNTS=".\Administrator" 
AGTSVCACCOUNT="NT AUTHORITY\Network Service"
;INSTANCEDIR=c:\SQLServer

Here is how to use it:

setup.exe /ConfigurationFile=SQL2008R2InstallConfig.txt /QS /IACCEPTSQLSERVERLICENSETERMS

One thing is worth of mentioning: installer creates a directory called MSSQL10_50.MSSQLSERVER under your INSTANCEDIR for the default instance. For a named instance, say Instance1, it will be MSSQL10_50.Instance1. The installer adds the MSSQL10_50. prefix and it does not look like it can be helped.