After 3 years in my current company, I've convinced management to finally sweep MS into the rubbish bin and adopt Linux. We have 35 desktops now running Ubuntu, and most of our daily operations are web based. we run thunderbird as email client, FF browser, Open Office, and mainly all open source apps. The network protocols are the same as MS (TCP/IP) which we use here, and our voip system. Our servers run (have run from before I joined)Centos and Red Hat, with Apache as our web server software.

Our employees are quite happy with their computers running a lot faster, without much clutter, and obviously management is happy as we don't have to pay any more desktop licenses to MS, and they didn't have to hire a Linux expert as I already had the knowledge and for the same wage, the transition was done successfully.

Now, this is not recommended for all businesses, fortunately it's worked for us. First see whether MS software is primordial in your operations, and if your staff is change-welcoming, and also, a very important point, if you need to hire a linux expert to help with the transition and further troubleshooting.