I love it! It had been a while since me and my wife did it, but last week we decided to get to it, and it was great.
She's a 38D right now, so it feels fantastic. Lately though, I've been obsessed with her ass, so last night we had some awesome doggystyle, and I pulled out and came while fucking her ample ass cheeks. THAT'S another fetish I've had for a good year now. I'm really fortunate in that I have a spouse that's willing to indulge me as much as she does. I don't have many fetishes (pretty much just titfucking and assjobbing), but she's a great sport about it!
I think it's more the visual that excites me the most, although the feeling of cumming between some nice soft tits is pretty awesome too.
My wife may not get the same stimuli that I do, but she also enjoys it for the visual, and that I get so turned on by it, and the feeling she gets knowing that she made me cum in such a naughty way.