OK, so you're buying a retina display MacBook Pro. Let's look past the fact that a maxed-out MacBook Air is probably enough for most regular people, or that if you order a new retina display MacBook Pro today you'll have to wait a month until it arrives. Let's figure this thing out!
Now, not to belabour the point, but if you're a regular person who isn't going to be doing much rendering or high-end editing, you can probably get by with a dual-core Ivy Bridge MacBook Air and 8GB of RAM. So what you're looking at here, really, is some more oomph in your Diablo III runs with the discrete Nvidia video card and that beautiful, beautiful retina screen.
In that case, you want the 2.3GHz model with 16GB RAM and 256GB SSD for $2739.
Here's why: SSD storage is precious, and precious is expensive. But these days you don't need heaps of space on your drive, thanks to cloud storage services such as Dropbox, Google Drive and Skydrive. If you're thinking about your massive not-on-Rdio-or-Spotify music collection, or all those torrented movie files that you can't do without, well, you're just as well off sticking them on a USB 3.0 9400RPM external hard drive. Spinning drives are actually faster than SSDs for mass media archives.
And the RAM? Well, it's soldered on there, so you've got to decide now. And $240 for the bump from 8GB to 16 isn't too bad. Memory is one of the things that will give you tangible benefits that you'll be able to see every day.
If you're a professional user who doesn't mind losing out on the optical drive (no big deal) or the ethernet port (kind of a big deal), you may as well max out with the 2.7GHz 16GB RAM 768GB SSD model. While Apple's configuration markups have been pretty egregious in the past, they are pretty much in line with the market now. $600 to jump to 768GB internal SSD storage? That's about right. Maybe shy away from the $260 0.1GHz upgrade to 2.7GHz, which takes you down to $4039.
Of course, all of the retina display MacBook Pro configurations are shipping with 3-4 week delays right now, so you've got some time to think it over.