Just did a monster test on my server with the most recent build.
Current notes:
Mobs spawn in clusters. Overall, there are too many mobs in one spot, but not spread out enough.
They spawn right in front of you. A spider will spawn right besides the other spider you are fighting with a sword.
Spiders don't jump you. They sit next to you and you take damage.
Every arrow that hits you makes the sound of you getting experience. Maybe you even get experience.
Every arrow you shoot and that hits a monster gives you the experience sound, too, even if the monster is still alive.
Skeletons seem to shoot / aim a bit too slow. Usually if I assault one frontally on a mojang server, I'd get an arrow to the knee one time before I get close enough.
Endermen I'll completely ignore for now because they also spawn in clusters and don't behave anything like Endermen.
Creepers have a tiny explosion trigger radios. They will stand idle next to you and go SSssSSSssSs for hours if you don't hug them close.
Spiders don't seem to really climb or jump.
Monster density seemed to be too high in well lit areas.
Zombies don't move their arms to attack you.
I've never seen a Zombie that looked different in some way. Don't seem to carry items or wear bits of armor, ever, so far.
All these are purely random notes; monster mobs are not as important to me personally as tame animals just yet, but I thought this might help.
Safwat was testing along with me, he might have other or more conclusions.
Current notes:
Mobs spawn in clusters. Overall, there are too many mobs in one spot, but not spread out enough.
They spawn right in front of you. A spider will spawn right besides the other spider you are fighting with a sword.
Spiders don't jump you. They sit next to you and you take damage.
Every arrow that hits you makes the sound of you getting experience. Maybe you even get experience.
Every arrow you shoot and that hits a monster gives you the experience sound, too, even if the monster is still alive.
Skeletons seem to shoot / aim a bit too slow. Usually if I assault one frontally on a mojang server, I'd get an arrow to the knee one time before I get close enough.
Endermen I'll completely ignore for now because they also spawn in clusters and don't behave anything like Endermen.
Creepers have a tiny explosion trigger radios. They will stand idle next to you and go SSssSSSssSs for hours if you don't hug them close.
Spiders don't seem to really climb or jump.
Monster density seemed to be too high in well lit areas.
Zombies don't move their arms to attack you.
I've never seen a Zombie that looked different in some way. Don't seem to carry items or wear bits of armor, ever, so far.
All these are purely random notes; monster mobs are not as important to me personally as tame animals just yet, but I thought this might help.
Safwat was testing along with me, he might have other or more conclusions.