I personally HATE dual monitors.
That said, I do have a 24" Monitor I connect my MBP to sometimes but my MBP is always in closed mode.
Also, alot of times, I prefer to use just my MBP with a mouse connected.
My monitor is a 24" 1080p variety and its Matte, after looking at a Retina display so much, I almost hate the way the HP 24" I use is.