I like the MBP. It's a great piece of hardware. I don't think the retina display is the quantum leap in laptop technology that it's made out to be. I don't feel any particular need to justify my purchase by citing the need to have top-end specs, because if I need maxed out specs, I can get them in my desktop for an order of magnitude less money. I enjoy working from the comfort of my desk with my big monitors and my mechanical keyboard and my nice speakers (and frankly, dislike working elsewhere without them), so laptop vs desktop is a moot point for me.
What do you mean by "comparable"? The only decent quad core laptops in the same weight class are the Vaio Z, Panasonic CF-B11, and 14" EliteBook -- and with those (or any heavier modern computer) you have a 16:9 aspect ratio. If you need maxed out specs and don't want to work from a desktop, these are the kinds of computers you want to get. Take a Thinkpad T520, remove the optical drive, give it a 1920x1200 screen and the X1 Carbon's trackpad and you'll have a comparable laptop. Or if Panasonic would just go for the 16:10 screen ratio, you wouldn't even have to drop the optical drive.
It's attractive, it's got a great build quality, and it's decently fast. I can't really tell the difference (in terms of "omg, teh pixels are invisible") between the Retina display and my HP Envy's 1920x1080 screen, but that might be because I don't sit with my face six inches from the screen. Text looks better on the MBP, but I credit most of that to the fact that OS X's font engine just blows Linux's (I run Fedora 17 on the Envy) out of the water.
Despite that, my daily driver is still my Windows desktop, running an i5 at 4.3GHz, with an SSD for my OS and programs, 2TB of magnetic storage, and 16 GB of RAM. That particular setup ran me well under $1k. My actual dev happens on a Fedora whitebox on my LAN, again with an i5 and 16GB of RAM, which I built for about $400.
The retina MBP is a nice piece of tech, but it's not the orgasm-inducing Jesus-box that some people seem to think it is. I probably couldn't justify the cost of one versus the competitors if I were buying it for personal use.