The features listed by Avast include Anti-Spyware, Anti-Rootkit, IM/P2P Shield, Web Shield and more. Avast also comes with the ability to run a boot time scan...a great option.
In particular, I've been impressed with the web filtering capabilities. It's been able to catch a few different tests I've thrown at it, particularly fake AV programs which there is little AV detection for.
The user interface is relatively straight forward, although there are lots of different options which could cause confusion for an unsaavy user. Personally, I appreciate all of the available options.
Avast will run in the system tray by default. By double-clicking the icon the user will get an active view of what types of scanning is enabled and disabled. By clicking on more details the user can access a more detailed view as below. This shows the option to set the agressiveness of the program when scanning each protocol, or "shield". Even more granular control over each of the shields can be accessed by going to the customize button.
By right clicking the system tray icon the user is presented with many more options, including the Program Settings option. This will open into the window below, giving you full control over any other options.
Resource utilization for the program is inline with expectations. To save on resources you can disable shields if necessary. The web shield seemed to be the most resource intensive on my system, which I suppose is expected as the majority of my traffic is web based.
I'm currently running the home edition, which is free. There is also a number of fee based options available from Avast, including a professional edition. Avast also has Mac and Linux versions which is a great idea. As these operating systems become more prevalent more viruses and malware will be written for them, as was recently proven with the latest Mac DNS exploits.
More information available at http://www.avast.com/eng/desktop_protection.html
