These WD drives don't use Sata 6Gbps, and even if they did, that isn't the cause of the incompatibility issues.
The main issue is lack of support for 64-bit Logical Block Addressing. Currently you'd need a 64-bit version of Windows or Linux, or an Intel-based Mac to even use the drive. 32-bit versions of Windows don't support the GUID Partition Table (GPT) needed to work with these drives.
You would also need SATA drivers that support 64-bit LBA (AMD's recent ones do, Intel's don't). That's why WD is bundling a separate Highpoint SATA card with these drives for now.
Furthermore, most PC users won't be able to boot to these drives at all, since the BIOS can't boot to GPT-partitioned drives. Aside from Macs, motherboard manufacturers have been slow to switch to EFI. Once that eventually happens, then we'll be able to boot to these drives.