Streaming is still only on one aircraft I believe, but I've now tried the Samsung Galaxy tab in J. What an absolutely hopeless idea that is. All the downsides mentioned come true. I was lucky to have a seat spare beside me so used their tray table, but looking sideways was not conducive to a comfortable flight and the earphone wire is not really long enough. There is no room to have a meal and watch the tablet if you can't use the next seat. When you do have it on your table it's too low to watch comfortably for long and when handed to me it had 79% charge so I'm not sure whether they're supposed to be charging them when in storage. The content loaded at the moment was drivel so I gave it back after about 15 minutes. Seat back mounting is the only way to go.
Streaming and in-flight internet.....OK (provided it works).
Portable devices......not OK (prefer nothing at all, which at the moment, is the only workable plan).