Tim,
Glad your happy with Avast! You got the news before I did, so I will be powering up the laptop to update my copy of Avast.
As it turned out, I did get some testing done which you might find interesting.
One of the nearest competitors AVG detected the Eicar.com file immediately, but not the .zip or .com.zip or .com2.zip on the download. However, it detected and stopped any attempt to open the file in any configuration. Apparently, it only checks one layer down. It failed to stop me opening the Eicar when it was configured as a .txt file.
The same test was run with one of the leading AVs and it detected all configurations down to second layer.
I could not get my Avast to function abnormally and display the "bug" which the new version cured.
Needless to say, Avast is top dog as far as I'm concerned!