When they introduced the synthetic ball players (I think Steve Nash) complained that the ball was causing cuts on his fingers.
Having owned and played with a number of the Spalding official leather balls, I will say that they take a while to break in, and since these are new, that could be half the problem. Once they are broken in, they are awesome. Spalding also had years to make manufacturing changes to perfect the ball.
When Spalding's synthetic leather manufacturer went out of business, the TF-1000 was never the same. I'd have to imagine going to a different company, in this case Wilson, is going to cause some differences between the two balls, no matter how much they try and replicate the two, whether it is microdifferences in the pebbling, leather, weight, etc. The grooves are different on the Wilson, but it is easier to grip, but this may change shot a bit depending on release. I'm guessing by year end there will be enough broken in balls and players will have adjusted to the differences to get percentages back to normal. I have watched a lot of games this year, and it does appear players are shooting the ball long at a much greater variance in last year. Of course this is anecdotal as I have no data to back this up.
When the NCAA switched to the Solution for the tournament in 2003, it sucked. During the season we played with a series of different balls, as the home team could choose the ball at the time. The solution actually made our percentages rise, but the ball wears out quickly and under the thin synthetic material is a soft rubber carcass. We hated them. Small differences on a ball can make a big difference on the court.