No good tech guy would argue that 4 gigs of RAM is sufficient for a modern system. Why Apple even sells a machine with the option of 4 gigs is beyond me. The good thing about the low SKU machine is that adding RAM yourself after the fact is ridiculously easy and is so much cheaper than buying it from Apple. The 2012 Macbook Pro (non-retina) that I purchased this July came to me with 4 gigs, and is only officially, according to Apple, upgradeable to 8 gigs. Unofficially, you can put 16 gigs of RAM in the machine, the same amount the Retina can be configured to hold.
Corsair's Vengeance DDR3 1600 RAM will work just fine and cost you the same as 8 gigs from Apple. Unibody Macbook Pros are so easy take apart and install RAM into. I did it in my pajamas in 10 minutes before I was even "awake". Just be sure the machine is off fully, not just idling in standby mode.
With the default 4 gigs of RAM, I experienced some serious slowdowns when I had G+ hangout running along with another 20~ tabs, Apple mail, and a few terminals. That is a very average system load for what I do and my brand new machine was choking on it. After changing to 16 gigs of RAM, I was able to open up 166 tabs in Chrome, Apple mail, and type up this article with no problems. And there is still memory to spare.
Here are a few shots of the Macbook Pro that I took shortly after getting it. I apologize for the crappiness of the photography; I only had my phone to take pictures with.
