@Bass: Agreed 100%. C# has been my primary for over a decade now, but when we started using a Ruby application and I needed to tweak and create a plugin and etc., I learned Ruby. When I needed C and Java, I relearned C and Java. When I needed Linux, I relearned Linux. As well as the dozens of other languages and platforms that I've found a need to use over the years.
If you can't pick up a popular language well enough to do real work within a few days, you haven't done enough programming.