Finished installing Avast 5.0 (uninstalled 4.8 and then installed 5.0. No direct update available)
The latest version (5.0) sports a brand new UI, light engine, Intel i5 and i7 core optimizations for optimum performance, faster service start times for Vista and Win 7, NO SKINS and FEMALE voice over and sounds. The voice overs also have changed (The infamous “A virus has been detected” has been changed to “A threat has been detected” and the hysteric siren in the background is no more)
However, it reports a number of false positives, ex: If you are using Realtek AC97 on board sound card (if you are using P4 Intel 845/865 chipset, yes you have this) then your sound manager was most likely detected as malware and put into chest. (hopefully it will be corrected by next update).
Note that your Avast 4.8 registration key is valid for Avast 5.0
My take: Please continue to use Avast 4.8 for sometime and then migrate to Avast 5.0