Avast is a low powered power house when it comes to virus protection. First off I don't know if results are fully accurate as some of the virus links went dead sense the first part of the tests but after adding more it still did well.
Avast performance wise is not that bad as it runs at ~50mbs of ram while idle and does not very much while actually scanning. The software did well when I was surfing the net trying to download viruses using IE8 though on known bad sites the software would block the download of the known viruses not even giving it a chance to get in temp directory to do havoc. On top of that avast redirects you to their page telling you that you just dodged a virus and tries to sell you on upgrading your free version to a version with more bells and whistles. Though on the positive note avast did not allow me to bypass the block like some other virus scanners did when they did warn you about a site.
On scan it did not pick up any viruses which surprised me a little though sense it did block downloads it did not allow many to get a foothold. While in herins boot cd avira did not pickup anything though SAS did pick up 2 variants of a fake antivirus. While malwarebytes did not pickup anything spybot did pickup a pup that every other virus scanner also did not pick up.
Overall avast did well enough to go to round two with the other better virus scanners to go in to more testing. AV-Test.org has their results here if you want more information from their tests.
So far avast has done the best out of the virus scanners both detection rate, prevention, and performance in low memory situations.
Hope this helps and will do more testing later,
Local Tech Repair Admin