My 1.4 prime didn't have fungus, it was only dusty thankfully. However, I the first time I used TCW's services to clean lenses was back in 06 when I had to send some 30 year old manual lenses in for cleaning. These lenses were stuck in a spoilt dry box in a storeroom for about 5 years. Some amazingly, had no fungus, some had mild fungus and some rather severe. The ones with mild fungus managed to get cleaned completely without any traces left. Only 1 was so severly affected that it has etching patterns on the rear lens element and that was the Nikkor 105mm P.C f/2.5. After cleaning the rest of the elements were okay, just the rear element looks badly etched. However, surprisingly, it is still the best performing lens I am using, sharp wide open, very high contrast and bokeh. Only problem is flaring when shooting into direct sunlight, no problem with shooting into indoor lighting though. From the looks of it, it is optically bad and probably no one will want to buy it. So the only problem I can forsee is a lower resale value to your lens. If the fungus is not on the front or near front elements and can be cleaned off completely, your lens should be fine for all practical shooting use (not for those laboratory pixel-peeping). However, on the microscopic level where we cannot see just by visual inspection there would be some etching at the fungus "roots" the the edges of the element. Unless its very bad, it should clean off like new.
