It can be interesting to add a conjugateTranspose operation in MatrixCategory? RectangularMatrixCategory? and SquareMatrixCategory?. For example conjugateTranspose(a) * a will give a hermitian positive definite matrix.
(1) -> a:=matrix ([[%i,7], [6, 3*%i]])
b := map(conjugate,transpose(a)) * a
Determinant and eigenvalues of this matrix are always real and positive. For example,
determinant(b)