As a long time gamer I don't respect phones and computers at the table, they take much needed attention away from the game. I have/use a variety of apps on my phone and computer alike, but I use them outside of game play.
I just like the books much better, as a GM I flip through the countless number of books I have on hand, it just feels natural. Not to mention after having read through the books enough you can easily flip to the references you need.
You make one book and it's obsolete... Eh No. You can produce it as a series. The ultimate equipment is a wonderful resource, and yes plenty of new things have come out since that should be in it... but who's to say they don't just make a UE2? They easily could and I'd buy it, it's just more material in a confined space that I can use at the table.
I love the feel of a book in my hands over a cellphone.