They're new, they're improved yes it's Goa'uld 2.0. The Ori are everything that the Goa'uld wish they could be. They are dangerous to us, to the J'affa, the Asgard, the Tok'ra even the remnants of the Goa'uld. There is potential for crossover elements with Avalon. In short, everything that we watch SG-1 for.
Ben Browder continues to fit into his role as the new leader of SG-1. With our new enemy, the Ori, Daniel Jackson has a reason to stay. Teal'c is out of power in the new J'affa government so he will stay and Col. Carter will return to fight this new problem as soon as Amanda Tapping is back from maternity leave.
Claudia Black is a nice, different type of female character. She relates well with Daniel Jackson and has an irreverent air about her that Sam doesn't have. I wouldn't want her to replace Sam but she is a nice change of pace and I would welcome seeing her on addditional episodes after the first six.