it is fine but I think 8 GB is the sweet spot right now. OS X likes memory and is pretty smart about using it. Even more so under Mavericks. I average 6 GB usage just doing nothing special. I went with 16 on my rMBP (Haswell) for virtualization of multiple OS' and also for future proofing. The additional $$$ are not relevant over the lifespan of the laptop.
This. I feel like too few people think down the road.
Yeah, right now, 4GB is probably more than adequate. But what happens next year? The year after? I don't know about you guys but I don't want to be replacing my laptop every year, so I went for the high end now rather than repeated smaller purchases.
This is actually the THIRD laptop I've bought in the past two years. I got an Asus Zenbook (the PC version of an MBA) in February of 2012 because I wanted something portable with good battery life for work. Unfortunately after about seven months I realized that the lack of power limited my ability to do anything else. So, not wanting to put the Zenbook to waste, I got a Lenovo y580p, a big clunky gaming laptop.
Fast forward a year. The Lenovo's low resolution makes doing work on it annoying, and the plastic build is chintzy. Meanwhile, the Zenbook has so little power to it, especially when unplugged, that doing ANYTHING with it other than using Office was impossible.
So I go to BB on Black Friday since MBPr's were $150 off. I pick up the Iris-only model, figured it would be "enough" for me. After a few hours I realized that it would replace the Zenbook fine but I'd need to keep the Lenovo because it couldn't play games.
Finally I had enough and went back, returned the MBPr, got the high end model and was just done with it. No more buying the lowest model I think I can get away with, no more constant replacing and feeling down the road like I'm stuck with less computer than I need.
If money is REALLY at a premium for you and you need the retina screen, and don't think you'll be doing any graphics-heavy tasks, by all means get the 8GB with integrated graphics. But as far as I'm concerned the best option is to get the most you can budget, that way a few years down the road you're still good.