It is effective.
Generally speaking, it's a sound delivery when the QB sees the backs of the defenders' jerseys. Particularly so if the safety runs shallow with a crossing pattern. Or in our case, it's very frequently open because Jimmy Graham draws the safeties on most of his routes. If you'll notice, most of the jump balls are thrown to the left. Graham most often lines up or operates on the right.
In these cases where there is little ability for a safety to read the pass and break in on the ball, then the WR has a natural advantage over a trailing corner.
It also depends on the talents of the receivers. Seattle has two really good options (Richardson and Graham) who are very strong hands catchers above the numbers. McEvoy is kind of decent at it. Willson is not very good at it. Baldwin -- I don't think there is a catch he can't be great at. Kearse, when he was here, was ok at it but generally allowed balls to get into his body too much to feature this delivery. Lockett is similar in that his hands are both small and he doesn't really catch high passes very well. Darboh looks like he's pretty good at that kind of pass too.
Not all receivers are the same. Some can make catches above the head naturally. Some aren't as good. We have good high ball hands catchers.
This delivery has a higher percentage of being caught, but also a very high percentage of the CB running into the receiver as they can't adjust to him pulling up or even stopping for the jump. So even where the balls are not caught, they very frequently draw a DPI penalty.
Ultimately, the percentage of a positive outcome can be far greater by underthrowing with some loft. The completion percentage to hit a guy in stride who has a step on a defender is lower. But one can get into trouble if they rely on that delivery all the time. Because DBs in this league study film too. And will be ready for that kind of pass if it becomes a dominant trend.
It's a valuable tool at an offense's disposal. Particularly so, if the QB is just having difficulty dropping the ball cleanly over the shoulder. Sometimes QBs just aren't as sharp as on other days. That's natural. And throwing a jump ball is a decent method for mitigating an otherwise off day.