I got a Seagate FreeAgent GoFlex 1.5 TB USB 3.0 drive from Seagate while at SXSW for evaluation.
The packaged drive comes as Read/Write for a PC and Read Only for a Mac.  To use it as Read/Write on a Mac you have to reformat it.  The instructions are very clear on the Seagate website.
Here are the formatting instructions:
http://seagate.custkb.com/seagate/crm/selfservice/search.jsp?DocId=207851
There are also instructions to download a utility to turn off sleep mode.  I did that too.
The drive comes with a USB 3.0 ( backwards compatible to 2.0 ) interface.
I also got a FireWire 800 interface.  This was very easy to plug in to the drive.  It booted with no problem on a MacBook Pro.