11" Air and 15" rMBP is excellent combo I think. I'm considering the same set up.
How much do you use the 15" versus the 11"? Do you use the 15" mostly on a desk or often as a portable too?
How's it for footprint and weight for typing with it on your lap and away from the desk?
Funny you ask that as I've been thinking about my usage lately since I got the RMBP.
I find myself using only the RMBP, but only because it's brand new and I smile every time I look at it. In a couple of weeks when I'm used to owning it, I'll start using my 11'' Air as I did again. Before my RMBP, I had a 15'' MBP that I used exclusively on a desk. I never moved it around, except for a rare use case where I'd need a larger screen. Anytime I'd need to do anything portable, I'd just use my 11'' Air. For example, on my bed, in classrooms, at the kitchen table- I'd use my Air exclusively because it's easier. I was also a lot more protective about my 15'' MBP as I am with my new RMBP because it's twice as expensive of a machine. That's part of the reason I don't like moving it around, because I'm afraid I might ding it. Also, on my 15'' MBP, I didn't like moving it because I've had several HDD failures in other notebooks stemmed from too much movement.
As far as footprint, the 11'' as well as the 13'' Air hit the sweet spot when not using a desk. Laying in bed, the 11'' Air is about as ideal a machine as I could imagine. This is also true about in class because several times you're forced to use a small desk, and the Air fits perfectly. Like I said, when I'm moving around I use my Air, and when I'm stationery I'll use my RMBP.
When you think about it, it would make more sense for me to have a desktop instead of the RMBP as well as the 11''. When you first think about it, a 27'' iMac coupled with my 11'' would be perfect. However, I for some reason dislike desktops. They feel last gen to me, because laptops are the future, and I just enjoy using a laptop much more than I do a desktop. I had a $2000 gaming machine pretty maxed out a few years back when I also got a 13'' MBP (my first Mac). I found myself using my very unpowered MBP compared to my gaming machine because 1) it was a Mac and 2) it's just a more enjoyable experience.
Overall, if you can afford it, I'd definitely recommend my setup of a RMBP and an 11'' Air. Both laptops have their strengths and weaknesses and when you use them each for what they're made for, it's the best possible setup IMO. The nice thing about my Retina is that if I want to use it mobile, which I do especially lately, I can move it anywhere and enjoy the display. IMO, for a college student, the iPad just doesn't accomplish much. An 11'' Air is 1000x more productive than an iPad, as well as being much more useable because of the keyboard/trackpad. It's almost as thin and small as an iPad as well, and IMO it's more comfortable to use, in any situation. Couple an 11'' Air with a RMBP and dropbox, and you've hit the sweet spot.
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Keep in mind the difference in memory the nVidia 650M carriers between the 2.3GHz and 2.6GHz models.
What do you mean by this? The 2.3 and 2.6 models both have 1GB GDDR5 memory.