I think developing races we only saw briefly in previous series is a huge plus for viewers. It was a backbone of DS9 and it is what elevated ENT in a lot of people's eyes. I love ENT regardless, but I know for a lot of viewers the Andorian development what kept them watching.
I agree,though I'm sure Jeffrey Combs had a large part of that. Still, it was indeed fun to expand on these races that we'd seen so little of. There really hadn't ever been an episode focusing on the Andorians on any other series, even TOS (remember the only notable Andorian character turned out not to be an Andorian at all!)
It was neat to see a modern-day interpretation of Tellarites, Tholians, and a Gorn as well, not to mention referencing aliens not heard about for years, like the Bynars.