Well, after giving the demo a playthrough, I think I'll put some of my thoughts on it here.
Being somebody who has experience with the Monster Hunter series, I dove right into Experienced mode. I tried out the Insect Glaive on the Great Jaggi, and while it seems like an interesting weapon, I don't really think it fits my playstyle. I was really hoping for a greater amount of control and interaction with the Kinsect (Sort of like a pet in other games), though it seems that all you can do is send it out to gather extracts from the monsters. While that's useful in it's own way, I still don't think I really understand the weapon enough to appreciate it's worth. For now, it just feels like another melee weapon to me, and kind of a clunky one at that.
After I beat down the Great Jaggi with my Insect Glaive, I decided to test out the other new weapon class on the Tetsucabra, being the Charge Blade. The Charge Blade seems like an interesting and fun weapon from the short experience I had with it, and it's a weapon I could see myself using in the full game. I never really used the Switch Axe in MH3U, so I don't know how the charge blade compares in similarity, but in my experience it was an enjoyable and powerful weapon. You use the sword form to rack up hits and fill the phials before switching to axe form, in which you can release the energy from the phials in a devastating combo. The axe combo deals a ton of damage, and it seems to have a high chance of knocking the monster down. I still need to work on switching forms more fluently, but the charge blade is a weapon I think I'll definitely spend some more time on
Finally, I challenged the Gore Magala, picking the familiar long sword for what I assumed would be a difficult battle. My assumptions were not wrong, as the Gore Magala is tough, at least the first time you fight him. Upon sighting the Gore Magala for the first time, I was instantly amazed by his design. I have to say, it is one of the coolest monsters I have seen. I'm excited to see what his armor looks like. The fight was long and tough -- the Magala is strong and fast, packing an arsenal of ranged attacks -- but I managed to fell him in the end. It was a satisfying battle, as I came close to death a number of times. If it wasn't for the massive stock of potions supplied, I'm not sure that I would have beaten it on my first try. I blew through all my Mega Potions and First Aid Meds, starting into the regular Potions before it died.
The game looks great on the 3DS, though I sometimes felt that some of the colors were a bit too bright and saturated, mostly the yellows and pinks. 4U feels much smoother than 3U, as there are less stops in movement. When jumping down from high places, you can still stumble forward instantly, unlike 3U where you would stop until you regained your footing. The platforming elements introduced add an interesting touch to the battles, and while I'd like to see even more free-form platforming in the next game, I think they did well implementing it into this game. The monsters in the demo felt a bit too easy to me as a whole, though I expect there will be harder monsters in the game to fill that niche. Maybe I'm just too used to G-Rank from 3U. The Gore Megaira was the only monster where I actually felt that there was a chance I might die at some points, though it didn't end up happening once in any of the battles. As I said, I believe there will be harder battles in the game, so this isn't really an issue. It's likely I'll be complaining about some of them eventually... All in all, the game seems very enjoyable, and I'm pumped for the full release.