What you propose is a very good computer, it is fast, light, small, has a very nice screen, and can drive a large monitor without problems. I considered one but did not get one because the battery-life is less optimal, the screen is too small for my ageing eyes and it is unsuitable for a continuous high load. It gets very hot and throttles down quite bit. But for things like Aperture, where the CPU performs in shot bursts, it is absolutely perfect.
Don't underestimate the integrated 4000 graphics processor from Intel. I use a MacBookPro retina and I normally switch to the integrated GPU, for normal use there is no noticeable difference with the discrete GPU (driving a retina screen!). Only for Video-rendering (which is done for a significant part by the GPU) there is a big difference. Battery-life with the 4000 is much better.
So: go for it, you will be blown away!