I gave the WiiU and 3DS demos a shot last night. I beat the rabbit three times between the two systems and had the time run out on the sea monster. Underwater combat continues the trend of underwater levels in every game I've ever played being terrible.
For all the talk about challenge, no "hand holding" and learning curves the rabbit with the dual blades (one of the recommended beginner weapons in this thread) was stupid easy. Just run up and attack until it dies, dodge often, and use one of the 20 (maybe more) potions you start with if you get hit. I assume in the real game you have fewer potions which would increase the tension. Not to mention the weapon might be a (over powered) late game version. I guess it’s fun to feel powerful but it certainly wasn't what I was expecting based on comments I've heard about MH, kind of a bad demo in that regard.
- Can you remap controls in the full game? Specifically L & R to ZL & ZR. I wouldn't mind switching A and Y around too. Personally if I can't use ZL I won't even bother with the game on the WiiU
- Anyone know how much underwater combat is in the full game and if you can avoid it? I'm sure if you play for 500+ hours you need to deal with it but for people looking for like 40 to 50 hours of hunting can you bypass it for the most part?
- How fucked are you for multiplayer if you play only a few hours a week? I’d like to pick up the game and give online a shot but if you play only 3 to 5 hours a week you’ll be behind everyone’s equipment in no time. I need like a busy parents hunters group or something
Well, the rabbit is classified as easy, it will most likely be an early monster in the game. In the demo, you're well equipped with strong weapons and armour (not quite endgame, but not beginner's stuff either) and well stocked, as you point out. In the full game, you only get what's in the blue chest at the start of a mission, and on the hard tiers, you don't get any items provided for you at all. So how many potions you have entirely depends on how many you craft in town and bring with you, you can decide how much inventory space you want to dedicate to healing items yourself. Additionally, Dual Swords are a good starter weapon with fast recovery time and quick dodging, so all of that combines to kind of a perfect storm to beat that monster and feel poweful if you have some modicum of skill.
That said, you can rest assured that the comments about Monster Hunter being a challenging series are not all conjured out of thin air!

You will feel challenged.
Some of the monsters do require underwater combat, but I felt Tri managed it better than other games. It feels like you're moving solidly around a three dimensional space, your moveset translating almost 1:1. But if you absolutely don't like it, you can mostly skip it, yes. There's always a variety of missions and quests you can choose from in every tier, and only some are mandatory. We all have our least favourite monsters and avoid them when we can.

Fuck Plesioth.
About the multiplayer, I can only speak from experience in Tri, where I felt I was moving slower than most people in the GAF thread, but never had problems finding people at various stages of my character's progression, lobbies are split up into levels so you can always find or start level-appropriate ones. There's a friend list, so if you find people in similar circumstances with similar time to invest you can coordinate with them that way. I guess it mostly comes down to the size of the playerbase, who knows how popular Ultimate will be, divided on two platforms as it is.
edit: another thing worth pointing out for all the people trying this out for the first time, is that the demo basically only shows one half of the game, the hunts. There's a whole other part to Monster Hunter with character management in town, equipment crafting, item crafting, companion management, the farm, merchant quests and harvest quests in which you don't necessarily have to fight a boss monster, but try to escape from them instead with an item (for example). They are big, long games.