Although this announcement comes as no surprise to many on the grapevine who have been reporting on it regularly over the past several weeks while most of the Rumors staff was on leave or sabbatical….many in the community expressed great enthusiasm for the new machines which form the backbone of Apple’s family of Macs.

The new iMacs sport an enclosure and display panels (20in 1680×1050 and 24in 1920×1200) which look on the surface, as well as on paper, identical to the previous generation but according to some of our oldest and most reliable sources at the highest levels within Cupertino’s Mac Hardware engineering division.

There is a lot more going on here than meets the eye in this latest update, even if you dig deep into Apple’s published specs so far.

The enclosure is now “internally ribbed” in key locations and has reinforced hardware at the “foot hinge” to improve the smoothness and ease of adjustment (while preventing “sag” or unintended movement from happening too easily) of the iMac’s one moving part.

There are also a number of tweaks to the cooling system, the placement of internal components over the last generation, and a change in materials for several small parts — one source suggested that all of the screws which hold the iMac together are now made of a different alloy which is “greener” from start to finish and is more easily recycled.

This is apparently part of Apple’s top to bottom “Green-ing” efforts and attempts to make its machines among the easiest and most completely recyclable in the world.

As for the display panels, set a new 2008 iMac down next to its 2007 counterpart, or previous generations of “whiteout” iMacs that preceded the current “black on brushed aluminum” model.

You’ll see a clear difference in display quality, according to our highly placed source and more than one other in the Asian manufacturing sector among Apple’s supply partners in China, most notably.