I bought a new 17 Gen 4 recently and took it to the range for the first time yesterday. It is an early 2015 model just like my other one. They were both test fired in April of 2015. For the first few mags, the empties were coming out of the gun about 6 inches out and at a very low arc. After a couple hundred rounds things were better, but very erratic. No BTF, though.
I went again today and put 300 more rounds through it. Ejection is decent, but erratic. On the last round of a few mags, the brass flew straight back over my head at high speed.
The other gun of similar vintage is not as erratic. As stated previously, it's the gun and not the shooter.