In other words, not very pleasant. But 4-EP also can leave a wine more astringent than wines without it.
A related byproduct of Brett, and a cousin to 4-EP, is 4-EG, 4-ethylguiacol, which can have a bacon/smoke aroma that some people like, but which some winemakers detest.
Oddly, Brett can also be used in making quality beer and often yields a fascinating complexity unlike traditional brews.
One fairly common spoilage component in white, rosé, and sparkling wines is called a lightstruck aroma, a sulfur-y note that affects wine and beer packaged in clear glass bottles that are exposed to various forms of light, especially fluorescent. (Such as in grocery refrigerator cases.)
A photochemical reaction creates a sulfite-y aroma similar to a skunk, shallots, or garlic – or occasionally urine. This can happen in any wine or beer bottled in clear glass. This risk is one reason why so many quality beer and wine producers avoid clear glass bottles (called flint in the industry) and resort to dark brown (amber), dark green (dead-leaf), and even black.
Roederer Cristal, one of the finest of all French Champagnes, has traditionally been bottled in flint bottles, but to protect the wine from lightstruck aromas, the company, wraps each bottle in a colored cellophane “robe” to combat lightstruck spoilage.