net.Buffers methods are on pointer receivers and it seems like the implementation of the methods immediately dereferences it. This seems odd since a slice is already a reference. I think this can be done without breaking compatibility. Concretely, this becomes frustrating if converting from an existing [][]byte:

var w io.Writer
var x [][]byte
err := (*net.Buffers)(&x).WriteTo(w)

Although I realize it could be written as:

var w io.Writer
var x [][]byte
y := net.Buffers(x)
err := y.WriteTo(w)