It is seen as a viable client OS, and one that can be made as thin or fat as you like. A diskless workstation a very thin client. The fattest client is a not really a client at all. The stage three business will come to grips with its choices it, seeing the value of competition and the resulting innovation. This is not to discard the notion of standards.
Standards are important where they apply to issues of interoperability.
Ironically, you know you're not in stage three unless you can think beyond Linux and also include FreeBSD and other open source operating systems in your IT tool box. If Linux becomes the only solution in the same way that Microsoft was the only solution, your business hasn't learned. If you think your company has achieved open source enlightenment I'd like to hear from you.