Sandbox Pros and Cons

Can someone tell me what’s the pros and cons of using a Sandbox? I know that using a Sandbox would isolate the program from the system to protect against an attack. Sounds good. But what are the cons? Does it slow down the program? Use more memory? Any info would be helpful. Thanks.

Personally I can’t think of any cons. As I see it anything that will protect my machine is good. I do have one question, have you read the help section? The help section can be accessed from the UI. I run Firefox in the sandbox and I have not noticed any slowdown. A little more information from you will assist us in answering your query. What OS are you using and what other security software are you using and which version of avast are you using (free,pro or ais)?