WOW! So you use MSE simply because it's bundled in the Windows Update for free?? That just comes to show me what an experienced user you are!
1) There are a myriad of FREE AVs that are way better than MSE, take avast! free Antivirus which even rivals many of the paid AVs according to test tesults and has an auto sandbox feature! Then you have Avira Antivir with its excellent detection rates, another is Comodo Internet Security (FREE), and the list goes on. So your excuse that you use MSE because it's free is just basically saying you are too lazy to spend a minute or two to download a real antivirus risking your entire PC's security.
Another sample I harvested last night:
VirusTotal scan result And on any given day, it could be MSE, or Avast, or any of 30 other vendors that don't detect the sample. In this case, it was the BlackHole launcher, which if successful, would then evaluate my system for methods of exploitation (does it have Java, does it have Flash Player, does it have Reader? Which versions? Ok, let's try these seven exploits). If the exploit were successful, it would then download or construct a payload file and attempt to launch it. Possible outcomes include a ZeroAccess rootkit.
The moral of the story: don't rely on antivirus software alone. As I mentioned earlier, Flame went scott-free for over two years in the face of every antivirus vendor on the planet. Sandboxes, behavioral detection, heuristics... you name it, it failed.
2) You have never had a virus with MSE? Sure? how do you know? if it doesn't detect the virus, how do you that you are virus free? why does it always get the lowest results in real world AV comparative tests and others? Why do some tests omit MSE totally? One just has to wonder.
I realize you're replying to someone else, but in my case, I periodically do boot-CD scans with another vendor's product as a checkup. I generally use Kaspersky, with all settings maxed out. As for your AV-comparative claims, you might want to verify your facts, since MSE is mid-pack. There's definitely worse performers out there. Given that a lot of malware is unique one-offs that are constructed on the spot and only served one time, look at the proactive tests.
3) Microsoft has always been crap when it comes to computer security, the most insecure web browser, IE, Windows Defender, a wanna be anti-malware program that never works or detects anything, and now MSE, since when did Microsoft have experience in creating an Antivirus? 2 or 3 years ago? No thanks, ill pass and stick to a product from a well known company such as avast or Avira or even AVG for that matter.
2001 called, it wants its outdated information back I'll grant you the criticism on the old Windows Defender, which Microsoft bought the entire Giant Antispyware company to obtain. It was never worth much. But IE is now quite good, and Microsoft as a company is recognized for its security program. For as much backwards compatibility as they maintain, they're doing OK.