I agree, it will be interesting to see how it all works out, and also on the being slightly in love with Dexter part..
But just because they're not blood related it shouldn't make a difference. For me, if you're raised as siblings, you are siblings. I don't know, just get angry at the writers for pushing this and would actually like more feedback from others as i can't be the only one who is so uncomfortable by it. I mean think of it this way, if you found out your brother/sister was no relation to you, would it be alright to bed 'em? not in a million years for me.
Besides this only really becomes a problem if the writers make it so the feelings are mutual. In which case it's a massive error as Harry is Dexters way of life, and HE considered them brother and sister. Just don't think Dexter would betray Harry like that.
Oh and on the, hoping Dex kills LaGuerta thing. One thing i've often found myself doing with this show when i've come across a character who's started to piss me off, my first thought is always "i hope Dexter kills him/her".. Always thought that aint a healthy way of thinking but glad to see i aint the only one