If you're in the market for the new iMac, it may be worth it to pony up to the 27-inch iMac if upgrading your RAM is a priority.  According to the Apple Store website, user accessible slots are a premium available only on the larger, pricier edition.  As tear-downs show, smaller, thinner devices become harder to replace or modify.

The 27-inch iMac is upgradable up to 32 GB of RAM, while the 21.5-inch iMac is Apple factory-configurable to 16 GB (8 GB standard on both models).  You can always pay the big bucks to have Apple upgrade the RAM before they ship it off to you, but those prices are a bit heftier than if you were to buy and replace it on your own.  At any rate, the 21.5-inch iMac starts at $1,299 before any configurations or sales tax, with delivery in November and December.

[via cult of mac]