Played the living heck out of Tri on the Wii, knew I'd have to upgrade when the servers went down. Have both the Wii U and 3DS versions.
It's a console MMO. Grind, upgrade and hang out w/ friends. Party up and take down huge beasts, or party up and go resource hunting for building new weapons/armor. It's all about animation priority like Demon Souls, too.
The demos were horrible, IMO. They just threw you into a mission w/ ZERO instruction. The full game itself doesn't explain itself; you have to dig online for info.
Most people will hate it. Power through the first 10 hours or so, and suddenly you're hit w/ this huge, LONG, amazing game experience.
Wii U version is the full package w/ online play and voicechat. The 3DS version doesn't have online, but can pipe through a free Wii U app to get online w/ both Wii U and other 3DS players, and includes streetpassing. You can also move your save between the Wii U and 3DS.