Andrew Cunningham at Ars Technica reports that the new iMacs are premium high-end kit, but lose important upgradeability options and have poor hard-drive performance.
Here's our biggest problem with the new iMac: making a laptop thinner and lighter is immediately noticeable. ... In a desktop computer, though, the pursuit of thinness at the cost of features makes less sense. The vast majority of the time, it's going to be sitting on your desk, and users will be interacting with a separate keyboard and mouse, pausing only occasionally to plug something in or adjust the screen's angle. Giving up desirable features like user-upgradeable RAM just to make a thinner desktop seems like the wrong move
Pass. That said, buying hard drives at this point is a false economy akin to asking the car dealer, "can I save 5% if you put in this diesel engine from a 1979 Oldsmobile Cutlass?"