it certainly is advantageous to work with non-proprietary languages like c#, boo, python or lua. they are usable in many other fields and so experience in them is a much more worthwhile skill to have.

with proprietary languages like lite-c, unityscript (it's not javascript!) or torquescript you are totally locked in. they also often can't compete feature-wise because they don't have the same manpower and communities behind them. in the case of lite-c i think the problems mainly are lacking oo and very weak debugging (not even a stack trace, crashes take sed down,...).