Ok so, I'll lay this out to the IT community. I'm a member of IT staff for a not-for-profit organization in Queens, NY and we are crunching numbers to revamp our entire IT infrastructure. This includes both client and server-side machines. We've got the client-side pretty much figured out as all machines are going to run Windows 7, considering we are in the midst of ordering some new machines but, I wanted to pose this question to you as a means of seeking opinion for options on the server-side. Before I list my options, consider that I am looking to centralize all user access, data, and administrative functions. I want group policy, user rights and permissions, as well as a means to manage all of that from a single computer.Are the words "Domain Controller" or "Directory Services" starting to float around in your head? if so, then I've put my point across. With that, i am looking for a means to manage and secure all network resources. Aside from that, fault tolerance and disaster recovery is a must. With that, enter Mac OS X Server, SUSE Enterprise Linux Server 11 with Novell Open Enterprise Server SP2 as an add-on and, Windows Server 2008 R2 in a domain environment. Keep in mind that there is no current infrastructure plan in place. Of these two, considering licensing stipulations, scalability, security, stability, and any other aspects that you can think of, which of the two do you consider a more cost effective candidate and are almost sure to provide reasonable ROI over time? I look forward to everyone's opinions and observations.