I'm avoiding it like the plague once the real meaty stuff comes out. I ruined SS in a way because I watched everything like a crackhead. There were no visual surprises left for me to discover.
Not E3 footage but when Nintendo starts going crazy with releasing news then yes, I'd likely also avoid watching a Zelda Wii U direct because it will likely be like the Skyward Sword Fall Conference 2011 when tons of footage got shown.