od -

Security Essentials is, as you say, a full time AV, and is pretty good. I don't consider it quite as "complete" as the protection suite I have elsewhere, but the one I use isn't a free one.

gnu - If you're running Windows, Security Essentials is very good. A free program provided by your ISP isn't likely to be better, but may have features that are "peculiar" to your ISP. These "features(?)" can sometimes be helpful and other times .....(?). The key to a simple assessment is the name: Security Essentials. It doesn't pretend to cover all threats, but concentrates on (and may be better at stopping) the threats currently being found when the update site runs the Malware Remover.

Microsoft recently posted the claim that one of every fourteen downloads is malware or is infected with malware. (But I think that number probably comes mostly from the Facebook users.)

For a totally inappropriate comparison:

Apple to support staff: Don't discuss Mac malware. (An unconfirmed rumor, of course.)

John