I ground up about 35-40 lbs of ONLY brisket from trimmings from last year's comp season a while ago and we've been eating it regularly. Haven't made burgers yet, but have made meatloaf, meatballs, spaghetti, taco meat, enchiladas, etc. with it. Haven't noticed any problem at all.
Others will likely chime in, but I'm not sure what to tell you. Was it only the texture and not the flavor you thought of as "not as good as expected"?
Big JT's Smokin' BBQ Competition Team
MERRY CHRISTMAS BBQ BRETHREN!!!!