Not really. Compared to using separate languages on the server and client, I feel that using the same language makes it a bit easier because I don't need to switch "mode" when jumping back and forth in the code. Like, when working on iOS apps, I sometimes write `self` instead of `this`.
I have sometime seen the argument for Node of using the same code on client and backend simultaneously, but in practice I haven't found any use for that. The only big thing I can think of is form/model validation, but if you do ajax, you can just as well do all that on the server anyway.