It depends on how much of an audiophile you are.
for the most part, you won't lose anything, but of course, you are adding another 'device' into the mix which can lead to increases in jitter. As to go from Coaxial to optical, you do need to use a chip that changes the signal to a light based one.
The differences to most will be inaudible. But of course, the quality of the changer has an effect