The new range of iMac differs from the old, because Apple has decided to withdraw market model by 17 inches, now 20 inches is the smallest member of the range. Note that prices have fallen considerably, you can buy hours, 20 inches at the price of the old 17.
In general, the speed of processors have increased as the power of graphics cards, because now all models have an ATI Radeon. Improved also the screen, which is now brighter, such as portable sony and apple. Introduced a new keyboard very thin, with keys similar to those equipped to macbook.
Leaving aside the customization options, the apple offers four models, two 20-inch and two by 24 inches.

We see their features and prices:

iMac: 20 inches and Core 2 Duo processor at 2 GHz * 1 GB of memory ram
* Hard disk, 250 GB
* A SuperDrive for playing and burning CDs and DVDs, including double-layer 8x
* Radeon HD ATI 2400 XT with 128 MB
* Price: 1,199 euros

iMac: 20 inches and Core 2 Duo processor at 2.4 GHz

* 1 GB of memory ram
* Hard disk 320 GB
* A SuperDrive for playing and burning CDs and DVDs, including double-layer 8x
* Radeon HD 2600 Pro with 256 MB ATI
* Price: 1,449 euros

iMac: 24 inches and Core 2 Duo processor at 2.4 GHz

* 1 GB of memory ram
* Hard disk 320 GB
* A SuperDrive for playing and burning CDs and DVDs, including double-layer 8x
* Radeon HD 2600 Pro with 256 MB ATI
* Price: 1,749 euros

iMac: 24 inches and Core 2 Extreme processor at 2.8 GHz

* 2 GB of memory ram
* Hard disk 500 GB
* A SuperDrive for playing and burning CDs and DVDs, including double-layer 8x
* Radeon HD 2600 Pro with 256 MB ATI
* Price: 2,219 euros

The ram is expandable up to 4 gb el'hard disk up to 1 TB
They are already available in almost all Apple Store Italians while the time of shipment is estimated to five days.