Wii U prototype controller -- what we've dubbed "The WiiPad" -- the pixel counters at Golgotron estimate the screen to be a WVGA display, with video presented in 854 by 480 pixels. We're not exactly what you'd call "techies" (we leave that to our friends at Engadget), but last we checked, 480px high resolutions aren't high definition.
Perhaps you'd like to peep those fine pixels for yourself and get counting? Golgotron's got you covered. Just, ya know, clear your schedule if you're gonna. Counting to 480 takes awhile! ... Or about 480 seconds.