Asus S121 isn't part of Asus' Eee PC family of the devices, its heritage is very clear, but as it's using a 12.1-inch display, Asus doesnt' classify it as an Eee PC. Its design borrows heavily from the Eee PC S101 and the only reason it's not an Eee PC is because Asus decided not to add devices with screens over 10.2-inches to its Eee PC family of products.
The internals of the S121 are quite disappointing though, as it uses a 1.33GHz Atom Z520 processor, which of course is paired up with the US15W chipset and 1GB of DDR2 RAM. The model that has gone on sale seems to be the most basic version, as it only comes with a 1.8-inch 160GB SATA hard drive, although options of up to 250GB, as well as SSD options up to 128GB are available for a so far unknown extra cost.
Remaning features consist of 802.11b/g/n WiFi, Bluetooth 2.1 with EDR, a 1.3 Megapixel webcam, Gigabit Ethernet, a D-sub connector, a multi-format memory card reader, three USB 2.0 ports and two audio jacks. The only benefit we can see of the S121 is the 12.1-inch display with 1,280x800 resolution. The standard battery is a mere 4-cell unit, although Asus claims up to 8h usage from it.
At 1.45kg the S121 isn't much heavier than many of the chunkier 10-inch models which is fairly impressive considering the larger display, but then again, the 12-inch Samsung NC20 is only 70g heavier and overall seems to be a better netbook. Considering that the S121 with the 160GB drive will set you back a massive €605 (£543/$799) which is anything but cheap, the Samsung NC20 is something of a bargain, as it can be had for almost €200 less.
You can find the listing here