I use mental ray since 2004 and it quickly become my favorite render engine. I attended, as a lot of you, to his slow decline over years... I have opportunity to work with Vray for a vfx feature film. The pipeline is around Vray and uses many new features highly "prod oriented" that make our lives easier.
It was my first experience with this engine and I must unfortunately admit it made me realize that mental ray can never back up the hill... :neutral:
I propose you my little impression on all of that in this post.