I thought the new avast was to have a sensitivity option in between “normal” and “high”. Most customise the same/similar options as below so this would be a good default setting to add, making avast detect more “out of the box”.
scan files on open:
WS?,VBS,VBE,JS,JSE,HTA,WSF,WSH,SHS,SHB,HTM*
created/mod:
ACE,ARC,ARJ,BZIP2,CAB,COM,GZIP,PST,RAR,TAR,ZIP,ZOO,ECE
etc…
No,the archive scanning doesn’t work that way. It will treat them as normal binary files and will NOT scan actual content.
And the Normal/High Sensitivity was indeed changed.
Normal is now as High before (only selected extensions on open and copy/modify).
High now checks all files regardless of extension (on open and copy/modify)
I would really suggest not to put archive files into these boxes - it may have very bad impact on the system performance - not speaking of the fact that the archived files don’t be detected anyway unless you enable the corresponding packers in the resident protection task (Enhanced User Interface only).
I’m due to this confusion… :-\ :-[ 
Sorry.
I already updated it here:
http://forum.avast.com/index.php?board=9;action=display;threadid=4818&start=30
ok thanks
from your link should I still put these in “scan files on open” box?
BAT,CHM,CMD,COM,CPL,CRT,DLL,EXE,HTA,HTM*,INF,INS,ISP,JS,JSE,LNK,MSC,MSG,MSI,OCX,PIF,PIF,REG,SCR,SCT,SHB,SHS,SYS,VBE,VBS,WS?,WSC,WSF,WSH
Well, that’s better. I still think it’s a big overkill, but if you really want to scan almost everything, it’s your choice 
Thanks Igor… 8)
More than this is only scanning everything 8)