One of my daughters works in HB, so I've been there a bit including staying in a resort property for a period. And I have spent some time in two of the three marinas on my boat. Reading the link that Robert posted you will see that precinct (mostly the land, but boardwalk etc which affects the marina) is quite a mess. Whilst I hope it can be resolved soon, it is hard to see it happening as there are some difficult issues involved. There is a big risk to buying into real estate there. But for transients, or renting there, its pretty good. I enjoyed it a lot.
The broader region is justifiably popular with the land-based grey nomads, and the place has enough critical mass to have just about all the retail stuff you could want. Real estate in the broader area seems quite strong and secure, to me at least. Brisbane is only 4 hours away, with that time likely to shrink once Gympie has a bypass.
From a boating perspective, its at the top of the Great Sandy Straits so has access to all the fishing in those areas, although personally I don't like the murky water. Some reported croc sightings in the Mary River. However, HB itself has sandy swimming beaches, and its not that far across to the Western side of Fraser Island which also has clear water and good swimming. Its about 100nm up to Lady Musgrave and the Bunker Group, which are fabulous boating areas. If I lived there I imagine that I would have a trailer boat for fishing and day trips to Fraser, and use my larger boat for trips to the southern Great Barrier Reef (including the Swain Reefs) when conditions were favourable.