A few weeks have passed since Apple announced its new line of iMacs, which means we’ve had plenty of time to speculate about the product. One thing we thought long and hard about is the iMac’s backside. The new iMac is a lot like a lady straight from Sir Mix-A-Lot’s id. It’s so thin from the front it practically melts away, but once you get a profile shot … bam! Baby got back. (Ars Technica and The Mac Observer have the pictures that Apple doesn’t want to show you.) 

At 5mm thick on the edges, and 80 percent thinner than its predecessor, it’s the thinnest iMac yet, which seems to fall right into Apple’s obsession with size. The iPhone 5 is “the biggest thing to happen to iPhone since iPhone” and the new iPad mini is “every inch an iPad.” Before that, the iPad 2 was 33 percent thinner than the original. The first update since May 2011, Apple’s new iMac will be 40 percent less in volume. But all those savings exist up front. Where the stand connects to the body, however, appears nearly as thick as the last iMac, resulting in a bulbous backside. So, what is the junk in the new iMac’s trunk?

The updates to the iMac line aren’t just skin deep. The insides of the iMac now feature the Fusion Drive, a new addition to Apple’s hardware that couples 128GB of NAND flash with either a 1TB or 3TB hard drive. The Fusion Drive moves the files you use the most to Flash storage and the files you use the least often to the hard disk, resulting in faster startup times, faster app launches, and quicker file access. The new iMacs also are upgrading to Intel’s Ivy Bridge Core i5 and Core i7 processors.  

While the promise that each iMac is “individually color calibrated using an advanced spectroradiometer” sounds like a gimmick, the option to get NVIDIA GeForce GTX 680MX graphics, perhaps the best available for an all-in-one computer, is a definite plus for designers, cinephiles or graphics junkies in general. But what are iMac customers losing out on when they trade up to a thinner, lighter desktop? An optical drive to play Blu-Ray discs? Expanded storage? Being able to easily upgrade in the future? The answer is yes; all those things will be sacrificed for a slim body, and here’s why …

Some of the changes are skin deep – specifically the gapless, less-reflective laminated-glass face built using “friction-stir welding,” a technique ”that required unprecedented feats of engineering,” according to Apple. Switching to “friction-stir welding,” Apple’s Phil Schiller said the company figured out a way to merge the molecules of the aluminum to make it one piece. That sounds pretty awesome, but it also makes it impossible to actually get into the computer if you ever want to upgrade the RAM. Previous models of the iMac allowed users to unscrew a small metal plate situated between the speakers and the bottom of the iMac to bump up the  memory. But that option is no more. Because of the new slim body, and laminating the glass face to its LCD panel, three out of the four models are not upgradeable.

Of course, the one model that is upgradable is the most expensive, high-end iMac: the 27-inch 3.2GHz 1TB model with an NVIDIA GeForce GTX 675MX graphics processor configurable to 680MX. However, starting at a base price of $1,999 before the graphics upgrade, that’s a lot to pay, especially considering you could get a PC with the same (or better specs) for less money. Sure, the Dell XPS One 27 isn’t 5mm thin, but considering a desktop computer isn’t an item we buy every one to two years, like our phone or tablet, do you really want to commit to a non-upgradeable iMac for the next couple of years? 

What are the features you wish Apple had included in the new iMac?