To get this thread back on topic....
I have spent some time recently (a week ago) with a Sony 84" running an Oppo BDP-103 . Got to play around with the combination for hours; using different BR material, try the native blu-ray resolution, let the TV upconvert it, let the Oppo upconvert it, different display modes, tried 3D-mode using the passive Sony glasses, played video games on it...really gave them both a good workout.
Guys, depending on how far away you sit and the size of your screen, Quad-HD
rocks. IMHO, it's a
must-have for passive 3D. And the Oppo 4K-upscaling is superior and
very noticeable when viewed from 8 to 10 feet away, and obvious from closer up.
And native 4K content in 3D is like...
holey moley. Stunning. Gave me the Big Want.

Honestly, that Oppo player impressed me as much as the monster Sony panel. Together, wow. Now the panel needs to come down an order of magnitude in price, is all... ;-)
But that Oppo is worth it's price
now, if you are running a 4K display of any size, again IMHO.
So, 'need' it? For passive 3D, definitely. Got a big screen & close seating? Then yessir, 4K is for you.
'Want' it? Oh my, yes...