The 400GB Intel S3700 and SanDisk lb400s are both in a test rig now and I can see a Samsung SM843 480GB drives in another rig.
Both the 400GB drives in Windows say 372.49GB
The 480GB drives say 447.13GB
The difference then is 74.64GB so we have about 6.7% less space than the 80GB advertised difference.