Available in early July, the Little Big Disk Quadra uses a pair of drives in a RAID 0 configuration for speedy response. My personal concern is that if one of the two RAID drives goes out, you'd lose all of the data in the array. Although LaCie states that it's "Compatible with Time Machine", the Little Big Disk Quadra is probably better-suited as a scratch drive for video work on the go.
This is a tiny drive considering the capacity - the outside dimensions are 1.6 x 3.3 x 5.5 in. (40 x 85 x 140 mm) and it tips the scales at 1.4 lbs (650 g). You don't need to use the included AC adapter when using the Little Big Disk Quadra with FireWire 400 or 800, but you will need it when using the drive with eSATA or USB 2.0.
Some sites are stating immediate availability, but LaCie has confirmed that it will be several weeks before the Little Big Disk is available.