After completing the truncated story and cementing some of Shepard's major decisions, you'll dive into Mass Effect 3 proper. It's only BioWare's second game for Nintendo consoles (following Sonic Chronicles: The Dark Brotherhood for DS), and appears to have suffered no obvious reductions compared to previous versions. Based on what I played at EA's Summer Showcase Event today – a snippet from Shepard's battle in a training ground for biotics – the game's Unreal-powered looks and framerate are comparable to the Xbox 360 and PS3 games. (The PC, of course, has the upper hand over all of them.)
The Wii U version adds an exclusive weapon, the M-597 Ladon, to Shepard's arsenal. It can target up to six enemies simultaneously (all marked in red on the HUD), and unleashes a barrage of devastating homing rockets once you pull the right trigger. The Wii U's pad takes a few moments to get used to if you're usually grafted to the Xbox 360 controller (the X button is where?), but once you're up to speed you can glance down and use some of the new control options.