I agree with the above. From what I understand, the late-2013 update finally made the 13" rMBP a mature product, hence why it was so eagerly awaited. The 2012 and early 2013 ones were really limited by the Intel 4000 HD graphics, which caused lag and stutter while driving the Retina Display.
Sure, being a basic user, you may not notice it yet, but it will show it's age eventually. Per the sounds of it, you tend to keep your devices for a while - which is why the late 2013 model would have been a much better buy! Other than much improved GPU performance, you would have gotten much better battery life, a slightly thinner profile, and PCIe SSD. I would honestly return the old model and wait for a late-2013 to appear in the refurbished section, or try to get someone to buy the new one for you with educational/corporate discount.
If that doesn't float your boat, go for the Air. Just my advice.