Funny, I instantly got into Blackwater Park despite not being into metal at all at the time. Actually, I listened to Bleak on Youtube for the lulz... I thought I would hate it.
I can easily see someone put off by the growls though... if my parents want to hear an Opeth album because they're curious about what I listen to, I would probably give them Damnation.
Once someone at school approached me (aww, let's befriend the shy kid) and wanted to know what I was listening to on my ipod. It was Ghost of Perdition, and after listening to a few seconds she said, "Oh, you're into rock music..." and left. I never saw her again...