This is such a great concept I decided I would tackle it in my own way. I just used the ETag HTTP header to check if the file has changed.

on *:START:{ svini_update }
ON: *:UNLOAD:{
  unset %svini.etag
}

on *:SOCKOPEN:svini:{
  if ($sockerr) { 
    echo -s 14[4*14] 1Unable to Connect to mIRC.COM
    .sockclose svini
    halt
  }
  sockwrite -n $sockname GET /servers.ini HTTP/1.1
  sockwrite -n $sockname Host: www.mirc.com
  if (%svini.etag) { sockwrite -n $sockname If-None-Match: $qt($v1) }
  sockwrite -n $sockname Connection: Close
  sockwrite -n $sockname $crlf
}

on *:SOCKREAD:svini:{
  if ($sockerr) { 
    echo -s 14[4*14] 1Unable to Download Latest servers.ini File (read error)
    if ($2) { unset %svini.etag }
    .sockclose svini
    halt
  }
  tokenize 32 $sock($sockname).mark 
  if (!$2) {
    var %read
    sockread %read
    while (%read) {
      if ($regex(%read,/^HTTP/1.1 304  Not Modified$/)) {
        echo -s 14[9*14] 1You Have the Latest servers.ini ( $+ $calc(($ticks - $1) / 1000) $+ s)
        .sockclose svini
        halt      
      }
      elseif ($regex(%read,/^Content-Length: (\d+)$/)) { sockmark $sockname $1 $regml(1) }
      elseif ($regex(%read,/^ETag: "(.*)"$/)) { set %svini.etag.new $regml(1) }
      sockread %read
    }
  }
  else {

    sockread &read 
    while ($sockbr) {
      bwrite $+($mircdir,servers.ini.tmp) -1 -1 &read
      if ($file($+($mircdir,servers.ini.tmp)).size == $2) {
        svini_finish $1
        halt
      }
      sockread &read  
    }
  }
}

ON *:SOCKCLOSE:svini:{
  tokenize 32 $sock($sockname).mark 
  echo -s 14[4*14] 1Unable to Download Latest servers.ini File (socket closed)
  if ($2) { unset %svini.etag.new }
  .sockclose svini
  halt
}
alias svini_update {
  echo -s 14[8*14] 1Checking for new servers.ini File...
  .remove $+($mircdir,servers.ini.tmp)
  if ($1 == -force) { unset %svini.etag }
  sockopen svini www.mirc.com 80
  sockmark svini $ticks
}
alias -l svini_finish {
  .copy -o $+($mircdir,servers.ini) $+($mircdir,servers.ini.old)
  .copy -o $+($mircdir,servers.ini.tmp) $+($mircdir,servers.ini)
  set %svini.etag %svini.etag.new
  unset %svini.etag.new
  echo -s 14[9*14] 1Successfully Downloaded Latest servers.ini ( $+ $calc(($ticks - $1) / 1000) $+ s)
  .sockclose svini
}

Quick ninja Edit: Changed it so the etag doesn't get update until it finishes copying over the new server list.