I was also considering and test drove a 2014 Lexus GS 350 (for lease) and a certified pre-owned 2012 Mercedes E350 with Premium II package (for purchase). Both of these cars could not compete with the 2015 Genesis, in fact, they came up very short in many areas.
Congrats on your new Genesis, its beautiful.
As an owner of a 2013 Lexus GS that I really enjoy a lot, I'm curious as to what you didn't like about the GS and comparatively liked about the Genesis...
I shopped for a Genesis in 2010 before I bought a 2010 Lexus ES (purely because of brand snobbery), and am seriously considering the new Genesis to replace my GS when the lease is up next year. Haven't driven a new Genesis yet but hope to soon.