As with RO, DI or RO/DI, much of the quality issues with distilled water center around the maintenance of the purification equipment, and what materials the condensate comes in contact with after it's a cooled liquid.
In the case of steam distilled water - what is the material of the condenser, piping and storage vessels ?
How long does the distilled water remain in storage ?
Is there any chemical post treatment of the distilled water ?
Is the distilled water in continuous contact with metal piping, or is everything from the point of the condenser forward made of plastic piping ?