Thank you for clicking through my Apple Store button to buy your iMac.
Some information from OWC, currently tearing down the new 21.5" iMac:
See blog.macsales.com for ongoing posts covering this iMac.
Standard pre-configured 21.5" iMacs are, at the moment, immediately available for pickup in Apple retail locations. At the same time, ordering from Apple's website indicates 1-3 days for shipment of both base/standard config options which becomes 7-10 days with any customization. Base memory is 8GB across the board and $200 for Apple to replace that with 16GB (+ the extra delivery time).
The good news - iMac Memory is definitely upgradeable. The 2012 iMac 21.5" is also far easier to open up than its predecessor. Which is a good thing since you will need to remove the screen and logic board to perform the memory upgrade. The new design appears to make this very straight forward with the correct tools.
While the 21.5" iMac does come apart in a much more straight forward manner, there is a glue that must be heated around the perimeter of the screen to allow the screen to come off.
We will be reviewing various processes for providing this heat, but this is not going to be as easy an upgrade as first perceived. While everything inside is confirmed very easy to work with, getting the screen off to get inside is a little more of a challenge. We are going to look at several options, but this may end up being an upgrade best done by a professional or at the factory.
Later (Dec 6):
We do have the full solution now for upgrading memory in the 21.5". Our 16GB kit will soon ship with all the tools you need to safely remove the screen, remove the logic board components, upgrade the memory, and put it all back together right how it was.
Because Apple elected to use glue tape to secure the display to the iMac chassis, this is a more tedious process than it had to be and something that I honestly don't expect many will seek to perform.
We do have a rough video online here: showing the entire process and will shortly have one of our full-fledged installation videos posted with the step-by-step instructions. The complete installation kit, including the 16GB memory set for $119.00, can be pre-ordered here: and will begin shipping in a few days following the posting of the DIY 'how-to' video.
In my opinion, this is a lot of form over function with the 21.5" and one has to wonder how hard it would have been to just give us a hatch for this memory. This isn't an issue with the iMac 27" model; which not only Apple supported/approved for enduser memory installations, but also can have up to 32GB of RAM via four modules vs. the 21.5" maxing out at 16GB due to being limited to using two modules.
The additional memory capability and non-hassle of adding memory to the new 27" might be reason enough to hold out for the larger display model (as if the bigger display isn't reason enough). If you're ordering a 21.5" model and even though Apple charges a premium, I suggest you watch the video and decide if you're better off selecting having the 16GB option installed at the factory