Pros: Free, does some job
Cons: -slowing down system
-not compatible with some firewall's
-on some cases it is not possible to register free version to overcome 30 day trial
Other Thoughts: Avast is constantly improving,but with every update, i encounter new diferent bugs.Some Av vendors like example Dr. Web are not so spread,but in test,i have never seen any bug or fail. I know it's free,but there are some free solutions that have really small or near 0 amount of bugs and hiccups.