>>That is a good question Hilmar. I would add a little to it. How many professions are out there where the professional must follow what the client wants instead of what he believes should be.
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>>Do we go to the Doctor and tell him that the machine he is using for the ECG is obsolete?
>>Do we tell the engineer what are the best materials to build the supporting column of a building?
>>Do we tell the electrician that the brand of isolation tape He is using is no good?
>>Do we tell our accountants which brand of calculators should they be using?
>>Do we tell our arquitects which CAD program should be using?
>>
>>Shouldn't we, as professional developers, provide the client the software he requires regardless of the language used, as long as it complies with all client specifications? Why would us accept the pressure from the client on which tool should we be using?
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>I find this a very interesting comparison, and of course I think you are right.
>
>But yet, the question remains, how often does this undesirable situation actually happen? What are your experiences, for instance?

I never had this problem. I think that I've never mentioned to my clients which language I was using, but, my days of independent developer are way behind me, since I got a job as "Jefe de Sistemas" (MIS manager?, not sure the right translation) of a company in Buenos Aires, then I came to Canada and I never thought of being independent again, so I guess you'll get better answers from other people here.