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First, the sensible thing to do is see how much memory Apple specifies as required for Mavericks. Apple's OS X Mavericks specification page says that you need at least of 2 GB of RAM to run OS X 10.9.
If course we all know that numbers like that are on the conservative side. The number is likely based on some very average stress tests on the system and is designed to promote the widest possible adoption of Mavericks.
Instead, let's take a look at a company, Ramjet, that would like to sell you a lot of memory and see what they say. Here's what Ramjet says about Mavericks:
Although Apple's minimum requirement is 2GB, our experience has been that Mavericks is very memory intensive. For this reason, we believe users will see better performance with Mavericks if they upgrade to 4GB of memory at a minimum, with an even better performance with 6GB of memory in the machine.
I believe that reasonable person would agree that extending the above analysis to 8 GB makes perfect sense. Apple, I would say, has selected a reasonable, indeed generous, amount of RAM for the average user.
What about Yosemite? The memory requirements for this OS are exactly the same, 2 GB. And so there's no argument that the new iMac will become obsolete due to the increasing memory requirements of Yosemite.
But What About Us?
The power users will, of course, say that it's a shame that the new iMac can't be upgraded. “The memory is soldered onto the motherboard. Ack! It must be an Apple scam! We cannot recommend this Mac!”
I disagree.
I counter that from my own experience, only a small percentage of Apple customers upgrade the memory in their Macs. If it's working fine, they don't bother. As we've seen above, the memory requirements for OS X aren't rising dramatically.
What's more, via the built in feedback mechanism of the Mac at System Preferences > Security and Privacy > Privacy > Diagnostics & Usage, Apple not only knows how many customers upgrade their memory, but the company also can diagnose how the OS is performing with a given amount of RAM. I'm betting that information was used to select the 8 GB number. Plus, I've used iMacs for years with 8 GB of RAM and never had a problem.
This entry-level iMac is just that. It's not designed for Adobe product professionals or computer scientists or people running Parallels Desktop. It's designed for the Apple customer who's on a budget and wants a quality Mac for the lowest possible price.
There's no arm twisting, and there are plenty of other iMac configurations to chose from, for more money, going up to 32 GB on a 27-inch iMac for more demanding users.
I am fine with recommending this Mac for beginners, switchers, and customers on a budget. 8 GB of RAM is four times the recommended minimum, and I expect this kind of Mac to be viable for many years to come.
And when it is time to upgrade because 8 GB of RAM isn't enough, the argument for the next step in future technologies, 3-5 years down the road, will make a new Mac very compelling. This 2014 iMac will be handed down or sold, and all will be well.