Safale S-04 does suck; I don't care for it either. Not only the taste, but the rock-hard cake of yeast in the bottom of my carboy was a pain to get out of it. It settled too quickly for my taste, and it just didn't make a very good ale. There was something "off" about the whole brew and I never could pin it down... Safale S-04 was the only unknown variable, and it was foisted onto me by my LHBS because they didn't have any of the yeast I really wanted.
It is difficult to say what is my least favorite style, but I'll have to go with any ales that are aggressively hopped at the end of the boil, or dry hopped. Our local brewery has a line of force dry-hopped beers called the "Dragon Series" and as a general rule, I can't stand them nor drink them. One sip and my tastebuds go into shock and nothing tastes the same, not even food or other drinks, until about 6 hours later.