Sorry, but then you really haven't looked at what's available recently. Near perfect HD titles are available for any tablet both legal and somewhat illegal (why limit yourself). And no IFE screen comes even close to HD, most have lousy hardware to start with but the software is almost always highly compressed.. and what BYO get's you your choice, no commercials and no editing because something might offend a poor soul.

And on modern tablets battery life is not a problem anymore, plus they are versatile for other things like e-books and the occasional browser session. At least if LH can offer Flynet with any consistency, I was 0 for 3 on my recent flights to/from the US and Canada :-(.