There were a few surprises in the launch of AT&T’s DirecTV Now last week, and the most important one was that the much-discussed rate of $35 for 100 TV channels is only an introductory promotion. That means some of the analyst warnings about AT&T’s paper-thin margins have proved to be exaggerated, but the loss-leading special offer could still drive strong uptake, with many US observers predicting that the service will sign 1m customers in “short order”. The underlying $35 deal is for 60 TV channels, and the 100-channel deal will go up to $60 after a while. This means the prices are more in line with everyone else’s in the US over-the-top TV streaming market. The service comes in three…