While you are free to visit the server with vanilla Minecraft the best way to experience the server is by installing the Shadersmod and one of Sildur’s shaderpacks.

I will do a more detailed write up in the near future but the 3 main components are:
Optifine to squeeze all the fps out of your graphics card
Shadersmod to give access to fancy shaderpacks
Sildur Shaderpacks to get that real feel going

You might also want to check out the MoBends mod which animates your character and spider and zombie mobs.