it\'s ok but i would change a few things like for ur on text event you have

on *:TEXT:$(* $+ %away.nick $+ *):#:{

it should be

on *:TEXT:$($+(* $+ %away.nick $+ *)):#:{

you have some of the amsg\'s silenced so it wont say it in the channel, and you dont have to use those halt\'s .
ok on ur gone aliases you have this:

alias gone {
  set %away.script on
  set %reason $$?=\"Type the reason why you are going away.\"
  set %away.time $ctime
  set %away.nick $me
  away %reason
  .amsg I am now away - Reason: [ %reason ] - Time left: [ $time ]
  nick $me $+ |Away
  halt
}

you can do this:

alias gone {
  set %away.script on
  set %away.nick $me
  away $1-
  amsg I am now away - Reason: [ $1- ] - Time left: [ $time(h:nn: tt) ]
  nick $me $+ |Away
}

same thing with ur back aliase you have this:

alias back {
  away
  nick %away.nick
  .msg nickserv identify %nick.pass
  .amsg I have returned from [ %reason ] - I have been away for: [ $duration($calc($ctime - %away.time)) ]
  set %away.script off
  unset %away.time
  unset %reason
  unset %away.nick
  halt
}

you can do this:

alias back {
  away
  nick %away.nick
  .msg nickserv identify %nick.pass
  amsg I have returned from [ $awaymsg ] - I have been away for: [ $duration($awaytime) ]
  unset %away.nick %away.script
}

look in to useing

$duration($awaytime)

instead of useing

set %away.time $ctime / $duration($calc($ctime - %away.time))

and look into useing

$awaymsg

instead of useing

set %reason $$?=\"Type the reason why you are going away.\"

also i would just unset %away.script instead of set %away.script off that way you can use that var like if (%away.script) { or if (!%away.script) { in the rest of ur script instead of useing this if ( %away.script == on )
id rate it a 4/10