If their prices are pretty good (which they should be as they’re a low-cost carrier), they should be able to add flights to many more destinations rather than just Portland and Honolulu. Another small-ish market that they should be able to fit into well is San Jose, which is among the largest markets Japan Airlines does not serve. They’d be competing with All Nippon Airways, but if their base is Narita, they will likely fly there, so it’s not a direct competition.
As a Portland local, it would definitely be exciting to see a 787 that serves PDX. Not sure about ZIPAIR’s business model, but I am curious to see how things pan out.