I've been having a lot of sharp-ish flavors, some almost plasticy and some not but sharp for sure, in my brews.......It just dawned on me last week that it may be from fermenting at too high a temp, so I just brewed up an Oatmeal Stout on the high end (1.062) w/ 2lbs of oats and my target for this brew is to make it as smooth as silk and eliminate nearly all "sharp" flavors (outside of the built in roastiness - I don't want it bland like a guinness draught or anything). to that end, I pitched two packs of S-04 and after 24 hours at 60-61 degrees it's begun a slow (hopefully steady) climb to the finish.......I'm going to try to let it secondary in the basement for a month or two before I bottle it, too, to further smooth it out.
.....My point is that I think those high temps really can add some funny off-ness to your brew. I have read like thirty posts here where people say their beer made the most dramatic improvements when they started controlling temps......I feel stupid that it took me 30 posts to absorb that!