Except I truly believe that Snape doesn't like Harry because of his history with James. Harry is just like James was as far as getting away with things (he's not as mean-spirited though) and I think that grates on Snape, plus the fact that Harry looks just like James. Snape will teach Harry, he will try and give him the skills he'll need to face Voldemort and the DEs but I don't think he likes him at all.
I understand all that, but Snape can't be stupid enough to REALLY believe that Harry is completely worthless. He's smart enough to know that there's a reason Dumbledore favors him.