I've flown with Hawaiian Airlines many times over the years both internationally and domestically, their service is quite good being the only major local airline in Hawaii and I've never had a bad experience with customer service or inflight crew as some have been claiming in their reviews here.
In saying that, I gave this a rating of 4 due to my own personal reasons below.
Checking in:
Upside: Check in is easy and simple once you familiarize yourself with the procedures, especially for a traveler such as myself who carries a Carnet for import/export of commercial goods, once I've got customs verification signed off (which required a visit to a separate building on the ground floor of the International Terminal) on my document then it's smooth sailing from there onwards.
The staff are always helpful with seating arrangements, they will move you to a another seat upon request only if available and being respectable and friendly towards the check-in staff always gets you great results with the possibility of a great seat, or even an upgrade for free.
Downside: Sometimes there's very few check-in staff available which will often make for impatient and grumpy passengers on the flight. Staff are not aware of what a Carnet is or what it is used for, perhaps some updated information or educating the staff on the procedure may save a lot of confusion on their part.
The ground crew can be a little rough with your baggage, throwing bags or equipment around when loading/unloading gets you a little anxious witnessing it when looking out of the passengers window.
Cabin Crew:
Upside: I was greeted with a huge friendly smile and a warm welcoming "ALOHA" by crew members upon entry into the aircraft who were all very well presented. The flight crew exercised outstanding professionalism towards my comfort during my flight and catered as best they could to my requests.
The emergency demonstration procedure was very detailed and explanatory, easy to understand, the P.A system was set at the perfect volume and not blasting my ears off as I've been subject to on other airlines which is an annoying experience to suddenly wake up to.
Downside: None.
Seating:
Upside: As I mentioned earlier, if you're friendly and respectable towards the check-in staff then upon request and availability you will be rewarded to an extra comfort seat or even premium economy. My recent booking had me in an extra comfort seat with an empty seat beside me of which I was thankful since I'm a very heavy set guy so having the extra room made my flight so much more relaxing.
Downside: Although you might have an extra comfort seat doesn't mean that it is. The extra legroom that comes with extra comfort seating is fantastic however, it stops there. It would be so much better if you could fold the armrest closest to the window up and out of the way just to reclaim the few more inches of space. The firm bump in the seat cushion gets a little uncomfortable after a few hours as it starts digging into the back of your legs, I had to raise my feet up off of the floor a couple of times during my flight to avoid the sensation of pins and needles in my feet.
Catering/Entertainment:
Upside: Snacks and beverages were served quite early after reaching our cruising altitude then meals not long after. Entertainment was also made available almost effective immediately after take off.
Downside: Personally I always take my own snacks aboard my flight as it seems more convenient plus I can choose a variety of which Hawaiian Airlines lacks. Their snacks have become noticeably budget which is a shame as it seems they've cut back on what snacks they originally served over the passed years. Bring back the Honolulu cookie.
The meals really do need an upgrade as they've become that undesirable over the passed few years that I've flown with them that I would prefer to not eat until I have reached my destination.
Inflight Entertainment is personal preference, don't expect the latest blockbuster movies that are out in theaters. The selection is good enough besides, I would rather get some sleep.
Apart from my own personal nitpicks mentioned above, I'll continue to fly Hawaiian Airlines simply because they're the most friendliest airline I've ever flown, plus their miles do not expire.