advanced triggers (e.g.: some useful stuff like changing basedamage, range, armor, "sliding" units, a votemenu (crashes game with wrong syntax) and updates of already existing triggers)
advanced items (no idea about that)
advanced upgrades (same)
advanced spells (whatever... never used)
mapprotect
"custom dynamic light sources"
tree units
hero glow models
multiple choice system
"all tiles buildable"
unlimited doodad scaling and rotation
"advanced melee ai scripts"
"hero selection system"
"multiboard progress bar triggers"
depending on the map one or many of those "features" can be added to a map. however i wouldnt recommend using it if you dont have to! if you get along with ur normal editor then stick with it. although weu adds certain useful possibilities (i couldnt live without advanced trigger XD) theres still a risk using it as some of those things might cause crashes, compile errors and other problems. always make a backup before editing a map the first time with weu (maybe it does that automaticly, but im not sure about this). u should also remember that you cant open a weumap with the normal editor.