It depends on what qualitys you are wanting to improve in the calves from the cows that you are breeding to. I have one 602 C daughter, bought from Stevensons last fall. She is about a 1450 to 1500 lb cow. I have her bred to EXT thinking that he will improvce the udder if she has a hfr calf. If satisfied I will bred to EXT again next year. Ext will clean up the udders, as well or better than any Angus Bull, besides adding style, feminity,and excellent quality.
I have never had any problems, but I have heard many others holler about EXT sons and daughters dispositions.