Most people don't use it like myself. It's just straining to the eyes and after trying it for too long like a week of playing.
I still can't get used to it sometimes but since i've been using my 3DS for years now like 2 years I think. If I'm into some games that have good 3D i'll turn it on.
But most of the time it's off. It depends really.
I'd say it's 50 50, some likes it on and some don't.

Well if you are looking for one without 3D that is always the 2DS but not portable la. 

Most game time was on Animal Crossing New Leaf around 300 hours and 400 hours for Harvest Moon A New Beginning.
Would recommend this games:
Fire Emblem Awakening
Luigi's Mansion: Dark Moon
The Legend of Zelda: A Link Between World
Pokemon X or Y
Bravely Default
Kid Ikarus
Rune Factory 4
Mario & Luigi Dream Team
Monster Hunter 3 Ultimate (Wait next year for MH4U)
Mario Kart 7
Mario 3D Land
New Super Mario Bros. 2
Zelda Ocarina of Time 3D
Shin Megami Tensei 4 (A bit hard kind of game)
Attack of the Friday Monsters (Awesome short game with awesome chilhood memories)

No. You buy you try and test la. This depends on your preference.

No update not opnly you cannot access eshop meaning you cannot play multiplayer or use any online function.

high 5, I am using it as well

that upcoming yoshi 3ds xl version very cute >.<

Jom

Mine is digital version so I don't have the demo code bro 
Only retail version gets 2 demo code to share with friends.

Wah I didn't know that
I've pmed you the code.
I'm keeping the other one for my friend.

The game has awesome review everywhere! It's a must buy.
You don't have to make Mii's. You can download them here http://www.miicharacters.com
I haven't even started the game yet. I'm still browsing for awesome stars and game characters for my villagers