I feel like so many of these use cases are romanticized.
Mapping on the phone is painful, especially if you have no signal. I tried it in LA and found myself waiting on tiles to load. I just decided to buy a small map and use my boyscout map skills -- which was better.
Amazon is great, but by the time I find myself in Best Buy, the decision to purchase has been made. Brick and mortar has the benefit of immediacy.
Same goes with tethering and immediate access to information. Coffee shops, office lobbies, and client offices offer all the connectivity my laptop could want. Secondly, I am not the kind of person to settle a dispute by whipping out wikipedia entry at dinner.
In terms of utility, I say it is definitely marginal. The times when it was convenient did not outweigh the expense.
Even if you're planning to buy brick and mortar, I find it valuable to be able to look at Amazon et al and confirm that I'm not getting ripped off (since, once in a while, I am).
Of course, you might still find that the utility is low :).