[ghshephard]

Mountain Lion 10.8.5 - fresh boot with only Chrome and this HN page open - Used: 2.83 GB.

Once the shared libraries are in memory, memory usage grows really, really slowly for my application set (listed above) on OS X.

I'm not saying that 8 GB will last forever - I'm just saying, as a power user who has zero need for more than 8GB right now, that 8 GB on OS X will be just fine for about 95% of average consumer use. Absolutely would not recommend upgrading an iMac's memory unless you are really certain you are going to hang onto it for more than 5 years - not the best use of $200.

I'm just talking about your average family use; for vertical niches (Video Work, Graphics Design, Heavy Industrial Programs, Databases) - obviously those people will assess their situation and make a decision that is optimized for their circumstances.