I would hazard a guess to say that the best way a person is more productive is by using what they are comfy using rather than going through the learning curvem however short or long that may be.

If I came into work and they had put a unix workstation on my desk, telling me its now company standard, then it would be my standard to resign. Not due to unix but due to the attitude of the company. Dont get me wrong I am looking at linux (I know its not unix, but it is a flavour) to use instead of M$ but at my pace.