This is a very rough guide to Hawaii, and it's mostly about Oahu/Honolulu. Those of you who live here (especially on a neighbor island) please edit this to match your experiences. I've also included links to all of my blog posts and their related references to other books, manuals, & newspapers.
I live on Central Oahu. We're about 20 miles northwest from Honolulu ("town") and we can be in Waikiki in about 45-60 minutes. (Traffic is more critical than distance.) However the island is roughly 30x40 miles (600 sq mi) so it's hard to get more than 90 minutes away from town. Kapolei ("Second City") in the west is just starting to grow, and in 20 years or so it'll be the second urbanized area. Oahu is currently building a light rail system to link Kapolei (Ewa Beach) to town (Ala Moana Shopping Center) and should be running by 2018 or 2019.
Average housing cost is all over the map. The median condo price is roughly $350K and the median single-family home price is roughly $750K. However high-rise studios rent for as little as $1000/month and some homes are as expensive as $6000/month. It's reasonable to budget $1500/month for an apartment and $2500/month for a single-family home, but the house may require a 40-minute drive to town (each way).
Indoor hobbies?!? This is paradise! Get outside! Oh, it's raining again? Well, there's always hula or martial arts.
Outdoor hobbies: everything you'd do on the Mainland, plus surfing. Wear sunscreen.
Weather:Like much of the island, Central Oahu's climate is 75-85 deg F year-round with winter lows in the 60s and summer/fall highs around 90. May-November is generally dry (with the threat of an occasional hurricane every year or two) while December-April (especially January) is rainy. However the island's microclimates vary from tropical forest all the way to desert. A couple elevations can get down into the low 50s in winter. The joke is that local meteorologists have the country's easiest job, and if you don't like the weather then you should walk a couple miles or wait an hour.
Favorite things: Surfing. Other island activities can be found at the website
101ThingsToDo.com. It's designed for visitors of all types but it's a good place to find the latest stores and vendors.
We enjoy Hawaii's multicultural population, especially the different cuisines. Waves of immigration over the last 150 years (mainly from Asia) have brought together many different cultures and nobody is a majority.
Least favorite things:Oahu is struggling with urban growth and the high cost of owning a residence. Sprawl is competing with the loss of agricultural land, and the island's future growth will have to come from high-rise buildings and walkable neighborhoods oriented around light rail.
Kilauea Volcano has been erupting continuously since 1983 and has spewed tons of sulfur dioxide into the air. Normally this gas is blown away from the islands by the tradewinds, but when those winds die down then "vog" (volcanic fog) permeates the air. It can cause respiratory problems for some.
Some temporary residents (mostly military on a tour of 2-3 years) complain about "rock fever" (small-town syndrome) and want a climate with four seasons. Others miss being able to drive hundreds of miles, seeing professional sports teams (of all leagues) in person, and NASCAR racing.
Mainland family (elderly parents, your grandkids) can draw you away from the islands. Some residents tire of having to fly at least 2500 miles to the Mainland several times per year for family or business.
Must try:This post describes a typical vacation itinerary:
http://the-military-guide.com/2014/05/01/lifestyles-in-retirement-hawaii-vacation/Stupid ordinances/laws:Hawaii culture (Chinese, other Asian countries) encourages fireworks at New Years Eve. This has extended to American culture on the 4th of July. Residential firecrackers and smaller displays can be lit at home with a $25 permit, but the law is widely ignored. Many residents buy illegal aerials and other powerful explosives. The noise, smoke, and debris are incredible.
Words of wisdom/advice:You have to live here to truly understand how you'll feel about a tropical paradise. At the very least you'll want to stay for six months as a resident. If you're considering buying a home, be ready to rent for at least 12-18 months while you sort out the neighborhoods and prowl for bargains.
Read these posts, and note the other blogs/books/publications mentioned in the "Related links" sections.
http://the-military-guide.com/2012/06/14/lifestyles-in-early-retirement-hawaii-long-term-travel/ Lifestyles in early retirement: Hawaii long-term travel
http://the-military-guide.com/2011/03/28/lifestyles-in-military-retirement-learning-to-surf-in-hawaii/ Lifestyles in military retirement: learning to surf in Hawaii
http://the-military-guide.com/2011/08/29/lifestyles-in-military-retirement-surfing-photos/ Lifestyles in military retirement: surfing photos
http://the-military-guide.com/2010/11/04/lifestyles-in-military-retirement-surfing/ Lifestyles in military retirement: surfing
http://the-military-guide.com/2011/10/13/lifestyles-in-military-retirement-living-in-hawaii/ Lifestyles in military retirement: Living in Hawaii
http://the-military-guide.com/2012/08/27/good-reasons-not-to-live-in-hawaii/ Good reasons NOT to live in Hawaii
http://the-military-guide.com/2011/05/16/lifestyles-in-military-retirement-haleakala-crater/ Lifestyles in military retirement: Haleakala Crater
http://the-military-guide.com/2011/05/30/lifestyles-in-retirement-haleakala-crater-redux/ Lifestyles in military retirement: Haleakala Crater redux
http://the-military-guide.com/2012/10/29/3d-hawaii-right-here-on-the-blog/ 3D Hawaii: right here on the blog
http://the-military-guide.com/2012/11/01/lifestyles-in-hawaii-tsunamis/ Lifestyles in Hawaii: tsunamis
http://the-military-guide.com/2013/04/15/lifestyles-in-hawaii-hawaii-island-the-big-island/ Lifestyles in Hawaii: Hawaii Island (the Big Island)
http://the-military-guide.com/2012/09/03/lifestyles-in-hawaii-naked-on-the-beach/ Lifestyles in Hawaii: Naked on the beach
http://the-military-guide.com/2014/05/01/lifestyles-in-retirement-hawaii-vacation/Sustainability:Hawaii grows less than half of its own food. You can do a lot with your own garden and fruit trees, which may produce 2-3 crops per year.
The islands are attempting to be 100% renewable energy by 2030. Oahu is at about 20% and Kauai is already hitting 90% on some days.
http://www.bizjournals.com/pacific/news/2016/02/03/kauai-utility-reaches-90-renewable-energy.htmlAll of Hawaii's potable water comes from rainfall that percolates down to artesian wells. The water supply is threatened by salt-water intrusion and residential construction.
One sewage plant is running a small project to reclaim and purify effluent for golf-course irrigation. I suspect that toilet-to-tap utility systems will be widespread within another 20 years.
Hawaii's sewage infrastructure is old, antiquated, and frail.
Over a third of Oahu's residences use solar water heating systems. All new construction is required to include this feature.
Oahu has one of the nation's highest per-capita uses of photovoltaic grid-tied electric power. Nearly one-third of the single-family homes have PV systems and a net-metering agreement with HECO. There are over 77,000 PV systems on the island.
http://www.bizjournals.com/pacific/blog/morning_call/2016/01/hawaiian-electric-has-77-000-installed-solar-pv.html