Does Microsoft Essentials work with AVG?

I did my research before I installed Microsofts's Essentials and they recommend you uninstall any other Anti Virus programs prior to installing theirs. Rather than uninstall my AVG, I disabled it, just in case I wasn't happy with Microsoft's. Works for me. Haven't seen a need to re-enable AVG, even to see if they play nice with each other, On the other hand, how does one really know if your Anti Virus program is really working?