Please now see http://msmvps.com/blogs/bradley/archive/2012/03/08/quickbooks-2012-on-sbs-2003-revisited.aspx
The system requirements for Quickbooks 2012 installs .net 4 – additional software: 250 MB for Microsoft .NET 4.0 Runtime, provided on the QuickBooks CD. Due to this you need to be aware that while it won’t mind at all being installed on SBS 2011 (standard or essentials), it will barf big time on SBS 2003 — see – http://blog.chrisara.com.au/2008/08/net-framework-35-sp1-issue-with-windows.html
Quickbooks 2011 also won’t mind SBS 2011 era servers. Start going back too far where Quickbooks installs .net 1.1 on the Server 2008 r2 platform and you’ll see issues.
So if you are rolling out Quickbooks 2012 anywhere, be aware that it would not be wise to be installing it on SBS 2003.