Avira + MSE is a winning combination.
The only drawback of MSE that I am aware of at the moment is that it doesn't give as detailed of info as AVG, Avira and others in regards to what is found when it does find an infection... or perhaps that one has changed since the initial release, I'm not 100% sure.
Also, if you already have Windows Defender installed, and don't get prompted to do so by MSE, or if it doesn't do it automatically, it's best to remove Windows Defender upon installing MSE.