[yuushi]

Which languages makes all the difference. It's more important to know at a language from a broad number of paradigms, rather than knowledge of a bunch of C-syntax-derived object oriented languages (I say this, but I'm just as guilty of it as many others, despite trying to rectify it).

Frequent usage is more difficult, though. I'd like to think I know C++, Java, C and Python all very well, SQL to a reasonable level. However, add the "dabbling" languages: Racket, Haskell, Scala, C#...where exactly would the time for using these frequently come from?

Arguably, languages are only important to an extent - libraries surrounding languages are the truly important part.

[tracker1]

I think knowing a given language can help a lot... for example the addition of generics and lambdas to C# has dramatically changed how I may approach a given problem in C#.

I know there is often a cost to using, for example the linq extension methods, it will look cleaner a lot of the time than the loop syntax.

Beyond this, simply using a new framework in an existing language can shape your views... for example, the differences in using JS with say jQueryUI, NodeJS, or AMD modules.

Knowing a language, and some platforms/libraries/approaches can greatly shape how you use that language. I once saw a VB app written by a COBOL convert... well, it ran in VB, but definitely looked like a COBOL application.