For me the abdominal hair has to match the amount of chest hair. I dated a guy who had a hairy chest, so the amount of hair on his stomach wasn't a problem. I've also dated a guy with no chest or abdominal hair and I didn't have a problem with that. My current SO has minimal chest hair so his happy trail is perfect for the amount of chest hair.
I'm a moderately hairy guy. Not Robin williams hairy, but plenty. back too. heck, all over. Some days I just want to wax it all off. I don't like to trim because that itches (I've tried). all or nothing.