That comment from LeCun is very interesting, because this means he moved from his own language, Lush, which he maintained for many years, to Torch7. And LeCun has very high standards for expressiveness and efficiency.
Oh, dont get me started about Lush :), this is my personal opinion, but I tried to use lush for a bit, and I ran away as fast as I can. However, in retrospect, that's probably because it was the first functional programming language that I was introduced to.
Also, torch has a great set of people building the ecosystem, lots of communication and collaboration online (github, forums, across labs) which lush lacked.
