Through the first weekend of sales, the iPhone 7 and 7 Plus are coming up short of the adoption rates seen in other recent launches. Here’s what our iPhone adoption trackers showed at the end of the day Sunday: At just 0.5% usage after the opening weekend, the iPhone 7 is at half the adoption of the 6s (1.1%) and less than a third of what the 6 had at the same point (1.8%). The 7 Plus is doing no better. It’s clearly too early to say the iPhone 7 is a flop. But despite Apple’s best efforts, the excitement level…..