As a newcomer myself (with over 70 hours in now), I wanted to chime it. Yeah, the demo is...perplexing to a newcomer, at least in my experience. I remember trying Tri for Wii; didn't get it. Then, when this came out, I downloaded the 3DS demo. I couldn't understand how this could be fun?
As months passed, the more I read about the game, the more I started to see the bigger picture. See, the demo just throws you right into a hunt without any of the massive context you need to understand how the game truly works. You don't know what the items are for or how they work; you don't understand why your stamina is draining in the tundra quest (if you even notice it). There's a very big work up to the larger hunts, and once you go through that process, the hunt itself makes more sense in terms of managing your stamina and items, and how to approach a large monster. In most games, you take enemies out quickly -- there's a lot of instant gratification. Here, there's a chase involved, trapping, a lot of stop and go, preparation.
The demo isn't bad, really. It's just very difficult to convey in a demo what the game is truly about and how it works.
And yeah. I'm playing the 3DS version, and it makes me wish I owned a Wii U. If you have a Wii U, definitely get that version. It looks beautiful, and online co-op is a huge, huge feature. Plus, though you can get used to the digital D-pad (or use a CPP) as I did, it's tough on the hands played on 3DS.