Splinemodel, I usually work from very basic shapes and simply use the transformation tools (rotate, skew, reflect and scale) and various Pathfinder filters (in particular, Minus Front and Unite) to create shapes.
In other words, nothing in the above iMac is actually drawn, believe it or not.
THAT'S the "secret".
I usually will draw a center guideline and work of of that, especially for reflecting elements and/or objects.
For the body of the iMac, I drew a perfect circle then simply selected the bottom point/node with the direct selection tool (the white arrow) and nudged it up to create that shape of "looking down toward a dome" perspective.
To make the drawer where the SuperDrive trays comes out, I just made a circle, used the bottom arc of it for the shape and cut away the rest by laying a rectangle box directly over it and apply the Pathfinder > Divide filter and got rid of everything but that simple "smiley" shape. I think gave it a fairly thick stroke with rounded endcaps and converted that shape to an outline (in other words, converted stroke to paths under the Object menu...great for things like that).
The display was just a rectangle box and an enlarged copy. On the larger copy, I applied the Rounded Corners filter. I then applied the Free Distort filter to "push" the top corners in a bit, giving the illusion of the screen tilting back a bit.
The circled vent holes were just a copy of the circle on top of the iMac where the arm meets the dome. I just scaled up a copy of the circle and applied a dashed stroke to it, experimenting with the dashes/spaces fields until I got that look.
The Apple logo? Type shift+option+K, convert to outlines, draw a diagonal line through it and apply the Pathfinder > Divide filter and color the lower right part of it a dark color and apply a lighter color to the upper left, to simulate an easy, high contrast chrome effect.
The arm of the iMac is just two circles joined together and elongated and placed in back. and overlayed with some light and dark shapes to emulate chrome again.
Honest to goodness, it's really easy. I think the true "secret" is to think of it in that way: distill it down to basic shapes and let the tools and features do the work.
Nothing above is "painstakingly drawn" with the pen tool or anything (I'm too lazy and scatterbrained for that!).
It's just knowing what tool or feature to use and, as I like to say, "thinking in Illustrator". Don't think like you would if you were trying to actually draw it with a pencil. Use the shapes Illustrator provides for you and simply tweak them with the appropriate tools and filters to get more complex, interesting shapes and forms.
Kinda wordy, I guess, but that's pretty much it. At least that's how I approach it.