It USED to bother me if the guy didn't get off, because I thought that was the whole reason why he wanted to have sex to begin with.
Now, it doesn't bother me in the least, because for the first time in my life, I can/have been, absolutely selfish about sex. It really gigs my bf. He's really okay when I 'use' him, but I still feel emotionally/spiritually 'safe' because it is him. I seriously doubt I could do this with someone I don't know all that well.
I am also very direct with him. I don't hedge, I don't say... "well, if you don't want to, that's okay..." I just tell him what I want, and I leave it up to him to decide if he wants to or not. If he does... . If he doesn't and I'm really horny, I go get my toys, take care of myself, and then cuddle with him after. I think that second scenario happened... once.
For him, it removes all pressure to perform... and conversely, it does the same thing for me when I get him off in some way, but am not getting off myself. If I want to get off as well, I make sure he knows it.
I suppose I don't measure successful sex by number of O's anymore... I measure it with how open and honest I am and he is... before, during and after sex. THAT makes for unbelievable sex...