Pros: Light, easy to use, easy to install, works ok with other programs, simple interface, non intrusive, daily updates, free, works well with 7,low false positives, no upgrade nags.
Cons: Slow full scan, buggy with XP, slow development, bombed in latest AV tests.
Other Thoughts: This review is based on MSE running on Windows 7 pro, on XP it was very buggy so i removed it from that machine.
MSE is a solid program, i have ran it for over a year now alongside Malwarebytes and have never suffered any infection. However it should be noted my browser is Pale Moon, i have removed many infections on machines running MSE with Internet Explorer which is useless in terms of security.
My biggest gripe with MSE is lack of development, i know that its meant to cover the basics but the program hasn't really moved forward since its release, in fact its taken a step back imo. I wasn't expecting tons of new features but i thought its scanner would at least improve, its still well over an hour to complete a full scan. It has also went from being a program with good detection to bombing in the most recent AV tests, this is strange given the size of database signatures MS has. I can only think that Microsoft are too busy sorting out that mess called Windows 8.
All that being said its still a decent program, run Malwarebytes alongside it and you have a decent defence, for a free setup run Threat Fire alongside it and you will still be more secure than many paid options. I love the no nag approach and the simplicity of the interface, you don't need to be a genius to set it up, the options are plain and to the point, very similar to Defender. The only time i have been alerted is when something worth alerting me about has happened. In one case i had a java exploit which MSE dealt with very effectively. One thing to note is that its set at default "not" to scan removable devices, i found this strange and not a good default setting. You can set auto scans for anytime and choose between quick and full. Quick used to be very quick but after a version update i noticed it scans many more areas including most drivers so quick scan takes approx 10mins now.
Installation couldn't be easier, double click the exe and follow the prompts. Be warned that during install it will switch on automatic updates by default, i never allow Microsoft to auto install updates so if you are the same then remember to switch them back off. It will do a signature update during install which is approx 60/80mb in size. When complete it performs a quick scan. It is also set at default to scan daily which i unchecked as i prefer manual scans. Another good option worth checking out is limiting its CPU during scans, you can set it to only use 50% CPU which is handy if you want a daily scan but wish to continue working.
Overall MSE is still a decent program, its one of the few AV's i have used that doesn't cripple system performance and you wouldn't know its running until something needs attention. I still wouldn't trust it as my only line of defence but it is only meant to cover essentials which it does well. With a little bit of development it could match its premium rivals but a can't see that happening anytime soon. I will stick with it though unless it gives me reason not to.....