I dont do much online stuff on mine so I cant comment on question 1. Question 2, does Netflix really vary that much from device to device? I wouldnt expect a Roku to stream netflix any better/worse than a Wii U or any other console. As for the third, the screen isnt horrible to use and some titles let you dictate how much you use it, in fact for some games it's pretty handy to have.
Wind Waker for example uses the small screen for your inventory management, maps etc so you never have to break into the actual gameplay to access stuff. Having a full dungeon map available at a glance rather than switching from the game to a separate screen makes playing more fluid.
The Monster Hunter 3 Ultimate game gives you the option of having all pertinent information appear on the small screen, leaving your television completely clean of clutter. Health bars, stamina, items, maps etc all are on the small screen which in this case is kinda annoying. Having to glance down at the controller just to see how much health you have was a poor idea, taking your eyes off an enemy in that game can be devastating. I went with the regular HUD layout for it (map/health on main screen, inventory on the small screen).
There's a slight learning curve when you first pick one up, but it doesnt take long to get used to.
edit - all that said I like my Wii U, but I love my Ps4, if you have a choice, buy one of those instead, you will be happier in the long run.