If you plan on opening the card, take advantage of their offer on the plan. They present it just before you land. We have the Hawaiian card and, for us, free luggage more than pays for the card.
On our last trip, we flew Alaska to Hawaii (point value for free trip was lower) and had the normal, indifferent, Alaska customer service. Our return flight was on Hawaiian and felt that service was the same or similar service to what we've experienced in the past. The big difference since the merge is that they adjust the flight times and types of planes quite a bit. It wasn't a big deal for us, but might be for someone else.