Most people use it in conjunction with Malwarebytes, using MSE as their real-time protection and making regular scans with Malwarebytes to double check their system for any malicious software.
If you read through the BSOD threads, then you'll notice everyone will recommend MSE due to it's lightweight nature on the system's resources, and it's compatibility and stability with Windows 7.
I have had no problems with MSE personally, and you probably haven't heard of Microsoft Security Essentials since it is completely free, and isn't attempting to sell you a product like the other AV suites available to use.