Got through a few more myself. I seem to be making slow going of this, but that's due to the fact I'm currently in one of my don't-feel-like-reading moods, not a reflection on what I think of the book

That said,
Indigenous Species might have been my least favourite so far. Not sure why, but I just never bought into the scenario it was painting. In a way it kinda reminded me of the woeful
Darkness Falls from
Bug Hunt - don't get me wrong, it was nothing
like as terrible as that, but I definitely got hints of a similar vibe here. I just thought it was a little immature. Still, it's the only one so far I've been outright disappointed by.
Blood and Sand was a big improvement. Not much story but very well written and I thought the child characters were really well-realised. Not entirely sure how a child managed to outrun a Predator at the end, but ultimately the quality of the writing was enough for me to overlook it.
Loved
Tin Warrior. Just a cool set-up and satisfying execution. Liked how single-minded the Predator was once it got off the leash. The author even managed to pull off the bit where it hijacks a Stryker.
If anything, I thought
Three Sparks was even better than the previous story. As happypred mentioned, Predators vs. samurais is one a lot of people have been clamouring for, so I'm really glad it didn't wind up being a disappointment. Loved the main character, and the sort-of twist at the end where the shogun bases the entire concept of ninjas on the Predator Hiroto killed was an amusing little detail.
The book is really on a roll at this point, because
The Pilot was excellent. Contender for the best so far in my eyes. Great setting, great characters, little bit of mystery and some very welcome (and genuinely funny) darkly comic touches. An unorthodox Predator story with a fantastic (and, again, darkly humorous) ending.