I really don't the sentence as "the best language to deploy across platforms", but as "it works across platforms". I started using Python on Windows machines,

I really don't the sentence as "the best language to deploy across platforms", but as "it works across platforms". I started using Python on Windows machines, and I was able to develop programs that run without any problem or adaptation on Linux servers. That include thing like GTK, making a GUI and working on Windows and Linux. It is possible that I could achieve that in other languages, I guess. But it had that capability, for sure... And for Dropbox that's a very interesting feature, as they have a client that needs to run on Windows, Linux and OS X...