its a total turn off, but if the guy has a great personality that would cover a little bit tha fact that he dresses badly..
i have like a thing for colour combination.. once I kind of liked a guy that was wearing an orange jacket (not a big fan of that colour but well) and when he took it off he had a yellow t shirt.. YES , YELLOW TSHIRT! I was like ..seriously?
but I repeat, if he has great personality and is funny and sexy in its own way.. I wouldn't mind the bad style (besides that's something that can be changed , haha xD)
There really are lots of degrees to this. Since you mention 80's in the answers, if a guy was wearing a Micheal Jackson leather jacket then yeah, I'd think he was stuck there. Same if he was sporting some acid-washed jeans (especially if they're tapered in that 80's way and almost white).
interesting answers however I would say that I am a guy who have absolutely no sence for dressing. and definitely don't know anything about trends. If it would be question for me I'd say that I would like to know that detail (even thro you say my dress sux it means you doesn't think same about me).
I think as long as they don't look like a slob it all depends on how important you consider their style of clothing is. As far as trends go who cares. Wear what makes you feel and look good. There's always someone who will you think you're outta style.