So, the first time I came (sans condom) inside of a woman I was kind of forced to do it. She kept riding me when I told her I was about to cum. She kept riding me harder and faster until my hips thrust upwards and I started shooting inside of her. It was the best orgasm I had up to that point!!!!!
And this is why the pull-out method of birth control is so unreliable because it is not only our own instinct to stay in until we've unloaded but hers too.
Back to the original question, "good" seems a bit tame, "Fucking fantastic" would more like it.
In more detail, for the primitive, animalistic part of our brains, an orgasm is always an intensely pleasurable however you get there but to be following your instinct in its purest form and to be so close to her as you bury your cock as far as it will go definitely adds something extra.
And I think Black Frost also has a point about the higher functions of our brain:
There's something both erotic and spiritual about it. The fact that she (or he, I suppose, but I don't get the same level of that with other guys) would not only allow me to put a part of myself into her, but also that she'd want me to leave something of myself inside her, afterward? That's...always been rather mind-blowing to me.
And for me the times we were trying for a baby were out of this world. Thinking that she not only wanted my sperm inside her but that she wanted one of them to meet her egg and become part of our baby that grew inside her was the best ego trip I have ever experienced.