In my experience, that can be comfortable on a part-time basis, but less so -- perhaps significantly less so -- on a full-time basis. I find myself overwhelmingly more productive with an external display. When I'm onsite, I typically use my rmbp lid-down with a 27" Apple Thunderbolt Display (2560x1440).
I actually am offsite a lot more than I am onsite at the moment, and maybe for the next couple months. I bought the low-end 15" rMBP to test it. 1920*1200 actually provides a lot of real estate while being quite usable. I'll see within the next two weeks how much it can increase my productivity. But it is really heavy.
Agreed on the gaming part. But one wouldn't buy a Mac to play games lol.
