You should. It has low resourse usage and I havent got a virus in the two years that Ive been using it. I liked it better than nortan, AVG, and Avast!.
Oh also, I use Zone Alarm pro and it dosent detect Avast as an antivirus, but it does detect Computer Associates. It may not matter, but it says that it monitors it and makes sure its doing its job. I like it!