Children arent really that important to me, but I supposed if the guy said "look, I cant have kids, ever." I'd have to think about wether in the future I might want them, and what it would do to our relationship if I did.
At the moment my feelings on the topic seem to be that I'll probably be swayed by what my partner wants, as I dont care either way about kids, so if I meet a guy who really really wants them, I'll probably have them, and if I meet a guy who really dosent want them or cant, it wont be any big loss to me.
I think if you love someone it would be really hard to walk away from them when they told you that, even if you really did want kids one day.
There are plenty of other ways though, like adoption and all the wonders of modern medicine and science. Im sure it would be a pretty big issue that would require talking, but at the end of the day, it wouldnt make me split up with someone I loved.