First off, I love it here. I wouldn't trade the experiences I have had at UH, both socially and academically, for the world.
That said, I understand a lot of the negative feedback I've read in other reviews. Moving to Hawai'i from the "mainland" does definitely result in some culture shock, and for some people it can be very hard to get over it. It was hard for me, especially in the first semester of my freshman year. But honestly, moving to a new place with a different cultural make-up from that which you are accustomed to is difficult regardless of where you go. I knew no one when I moved out here, which made the transition even more difficult.
But I got over it. It is not as daunting as many would lead you to believe. I am caucasian, and yet I have never had a bad experience with any "locals", nor do I think the sort of racism some of the other reviews have discussed is so prevalent. Hawaiians are people, just like you. However, they are proud of their culture and their islands, and rightfully so. Understand that, be respectful and you wont have any problems. Getting used to island life may take longer than your first semester (and it may not), but I think you should always wait a year at any school to decide whether it is the right fit for you.
Like other schools, the general education/lower division courses are not overly challenging. That's why they are lower level. Upper level classes vary in academic vigor, also like most schools, but most do require you to actually think critically. Ultimately, you decide how much you want to challenge yourself. This school is big on encouraging students to motivate themselves. Professors of upper level courses will not babysit you, they will more than likely treat you like graduate students; that is to say, like adults rather than teens. If that doesn't appeal to you, grow up. Or maybe go to a CC before you attempt ANY big boy school. If you actively take on a class and can find the motivation (whether from yourself, your peers, or your professors), you will be challenged and you will learn a lot.
I have had good and bad professors, mostly good, some great. Most are easy to approach and are open to out of class discussions/questions/emails/etc. For the most part, the professors are more concerned with your effort in the class and than with sticking to cold, hard grade points. They want you to learn, and your final grade usually reflects that. Thats not to say that there are not ways to BS your way through some classes; there are always many ways.
Don't like the way campus looks? Buildings too old for you? Good news, they are doing a ton of renovating. They're building a new campus center. I hear it will have a state of the art gym. Still not satisfied? Look up. You're in Manoa Valley, in Hawai'i, and there is probably a rainbow. Really so shallow that you need a big brick ivy-league type building? Go there, and enjoy the blizzards.
Socially, people are friendly. You meet a lot of people in the dorms, its a good experience for that reason, so I generally recommend it. That said, I got the hell out of there after freshman year. Lots of people move off campus, theres lots of housing, and you will undoubtedly know at least SOMEONE with a car or a house that they party in by the end of your first year. Most likely, you will know 5 or 6, excluding friends of friends.
There will be bonfires, beach BBQs, and sandbar parties (boat the mile off shore in kaneohe, drop a keg in the knee deep water, good to go). Triple Crown of Surfing goes off on North Shore and is super fun. Nightlife wise, you're a hop skip and a jump from Waikiki. Some bars/clubs close at 2, some at 4. Downtown has block parties for every major holiday, and they are glorious.
Walk far enough in any direction and you will hit the beach. Duh. Surf, swim, snorkel, tan, whatever. Its beach season ALL YEAR. And yes, we do study on the beach. Speaking of studying, in case you are so inclined, one of the libraries is open 24/7, and sometimes they have free coffee.
Scared of Island Fever? Wanna get away? Super cheap flights to the neighbor islands are easily found, and every island is different. It's pretty hard to come here and not find a way to see the other islands. Your friends will go with you, I promise. All in all, I've been taking 5 upper level courses, usually history or political science, for each of the last 3 semesters. I log my fair share of hours in the library, I do my shit, I pull damn good grades, and I learn enough to hold my own in debates with students of "more prestigious" schools. I'm not worried about getting a job or getting into grad school at all, whether I choose to stay in Hawai'i post-grad or not. But your college experience should be more than just going to school and getting good grades so you can get a good job. It's important, but come on. Go out and LIVE. Experience what its like to LIVE in Hawai'i. I suppose some people could get bored, but honestly... thats on you. You live where people pay ridiculous amounts of money to relax on the beach by day and party by night and you're bored? In my opinion, with all the options, it's kind of hard to do.