I do agree that 4GB is definitely not ideal for prolong usage especially when considering it is soldered together with the mainboard. 8GB would be the ideal RAM size. You will appreciate your investment when seeing minimal thrashing. For me who multitasks a lot, even 16GB on my MBP is barely enough when considering my MBP is running for 1 month. Though it helps with minimizing the page outs and swap.

Currently waiting for the next refresh for rMBP and possibly MBA with the rumored Retina display featuring Intel 5th generation Broadwell processor. The waiting will be worth it when I'm retiring my trusty friend MBP 13' 2011.