These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Nightmare Fuel: The headless dinosaur running around may seem amusing at first, in a highly morbid way, but then when it stops, slumps to the ground lifeless and trembling, spilling blood everywhere... yeah.
The very Gorn-y death of Jack. Ouch... Ouuuuuuuuuch...
In Episode 4, the female Troodonreturns to her nest and mate and nudges him, only for her mate to fall over. He's been frozen solid.
We see from the point of view of the young Protoceratops as one of the Velociraptor looms over its parents' bodies and starts feeding. Then it looks up straight at the camera. On its own, it's not that scary, but when you put yourself in the juvenile's shoes, it certainly is.
Special Effect Failure: The first episode is ripe with these, but a few particularly bad effects stand out, such as the "disintegrating" Inostrancevia and the fake lava splash, the Saurosuchus tail that very clearly phases into solid ground as the animal gets up, and the Zalambdalestes family who, instead of running convincingly, simply slide and turn in the air above the ground with their feet moving as if they were running in a straight line, and also disappear/reappear between shots.
The primary feathers on the deinonychosaurs in episode 3 frequently merge with the scenery and other animals.
The Devil Frogs are pretty badly animated.
The flock of birds during the last shot of Episode 4 looks like it belongs in an episode of Sesame Street.
Running animation in general is messed up. Most of the time, the animals just slide across the landscape, with their legs doing their own, independent jiggling. In fact most of the motions in episode 1 & 3 have a jarring artificial and stiff quality to them. Only thing missing is visible cursors moving the animals around.
Squick: We see a mosquito sucking blood from the eyeball of a reptile carcass.
The Tyrannosaurus use their feces to build a nest.
A Beelzebufo is stepped on by a titanosaur. (Also, the Beelzebufo has just eaten a young Majungasaurus, so we can somewhat make out squashed remains of the frog's last meal mingled with the squashed frog itself.)
Ugly Cute: The mosasaur babies. The Troodon, the Anhanguera babies, the Probelesodon, the Ornitholestes, and a variety of other critters stand somewhere between here and Ridiculously Cute Critter.
Visual Effects of Awesome: What the creators have been bragging about for quite some time, since the first snippets of information about the show had been released. They managed to succeed, partly. By this, we mean the look of the show clearly indicates that it had more than one animation team working on it. The first and much of the third episode was animated by one team, and while they're passable for a run-of-the-mill TV Documentary, the graphics sadly come off as quite pitiful considering all the hype. Thankfully, the other two episodes play this trope straight with some of the best looking TV-budget dino effects of recent times.
The Woobie: The lizard from the first episode. Killed by a bunch of mosquitoes.
The rooster Eoraptor and Gigantoraptor, also from the first episode.