Depending on what assets you're expecting the virtualzation to defend, this could easily result in a false sense of security.
Simply separating your "online habits" from your "offline habits" via virtualization will only go so far as to help protect one from the other. To better clarify, here's an example of a scenario in which the virtualization you've described could be a generally effective defense, and one in which it would not.
Effective: You have some personal financial records on your "offline" machine which you would like to keep confidential. Your "online" machine is infected with a Trojan via browser exploit. Presuming there's no data connection (file shares, network, etc) between the two, the data on the "offline" machine is probably safe.
Ineffective: You do your banking, e-mail, and shopping all on the "online" machine. Someone sends you a phishing message to which you become an unwitting victim, and the system is infected with a Trojan. All of your online account credentials can now be considered compromised.
Perhaps a better approach would be, instead of isolating "online" activities from "offline" activities, separate "high risk" activities from "sensitive" activities. Use one system for your day to day browsing and overall leisure activities, and use another for things like banking, shopping, and other sensitive things. Fully secure both systems as usual, and isolate them from one another as much as possible. Make sure that all activities on the "sensitive" system only involve connections to known-good and trusted networks.