BleepingComputer.com: how safe is Microsoft Security Essentials

I currently have Avast free and Zone Alarm free firewall on my pc, but I have heard a lot about Microsofts Security Essentials and installed it on my works pc - everything seems fine, but how safe is it and is it as good as Avast? It certainly doesnt intrude when it updates like Avast does.

Microsoft Security Essentials Overview is basically a stripped-down version of OneCare aimed at users who either can’t or don't want to pay for antivirus/anti-malware software.

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Microsoft Security Essentials auto-updates once every 24 hours and there is no setting within MSE to change the scheduled time or frequency. See the MSE Definitions/Signatures Update FAQ. However, you can always manually download the latest Microsoft Security Essentials updates from the Microsoft Malware Protection Center Portal.

Before installation, Microsoft Security Essentials checks for a validated copy of Windows and will disable Windows Defender. You need to uninstall all other "Memory Resident" antivirus applications before you install MSE.