A good quality spirit should be fruity, delicate, fresh, elegant and even have a hint of herbal tea and dried flower petals, it will gradually become more complex and layered as it ages. 

If the spirit has good acidity (without being overpowering), the style will be round and solid; if the acidity is too high, it will be flat, dry, rough and short on the finish.

For high quality eaux-de-vie, they may have a more perfect mouth feel, with a slightly soapy aroma, aromas of fatty acids, walnut kernels, plums, violets, etc. 

After ageing in oak barrels, spirits often take on the aroma of the barrel, such as vanilla, and the wine becomes softer. What's your favorite flavor of spirits?