This was one of the best games I have ever played.
It took me about 5 or 6 hours at best at the controls feel natural for this game.
It has completely no default HUD, which to me makes you feel just more immersed in the game. Even when turned on the HUD on offers an ammo counter which doesn't really do anything because your character can tell you around how many mag's you have left from memory. The game also offers no target reticule which doesn't really matter because of the auto-aiming feature, which is very hard to detect. You can also aim manually but I used this feature very little with every gun besides the sniper.
The graphics, lighting especially, were amazing. Shafts of light penetrate the upper levels of the jungle, while even in dark areas there is enough light to see sufficiently. There are some minor glitches in dinosaur movements, showing up more prevalently in the smaller dinos such as raptors and bats. Bat will occasionally 'warp' down from their sleeping areas and start flying around. Raptors can jump incredibly high, and this gets especially annoying in levels with stairs where you feel safe, but can be assaulted from above.
The ally AI is lacking, you will often find yourself blocked by them, or running out and getting themselves attacked. But even when they are getting attacked you hear a certain musical score and you know that your friend is being eaten. The enemy AI is fairly tough, the raptors especially are unrelenting in their assaults on your hiding spaces.
Overall this is one of the best first-person shooters ever for the PS2, and it even deserves a title of it's own due to its sheer innovations with the HUD, and environments.