MSE isn't as quick as AVAST to spot bad scripts on a web page, Google lists included. Can't run a scan before Windows loads and is a tad dire at checking cookies. I agree it's the best effort Microsoft have come up with but not good enough for me.
Have to chip in here and say MSE has been excellent for me too... it has detected a couple of problems in the last 12 months for me as I clicked on things. Not what you would expect to be dodgy sites either.
As many know my strategy is to keep daily backups so that if anything happens I just go back 24 hours. My reasoning is that even when a virus etc is removed, I believe (from what I have read) that registry keys can remain altered and compromised causing problem in future.
But back to MSE... it's been great and 100% trouble free. I think cookies are a bit of a non issue tbh... do a proper disk clean and they are gone. The last 12 months have been the least problematic of any for me with Vista, just using MSE and only Windows tools for housekeeping.
A proper disc clean. Well Ccleaner fails there. MSE certainly fails. Run SAS to see what adaware cookies are on your PC, some are Java based, if you have SAS that is. I'm certainly glad you've had 100% trouble free surfing.
Not sure about Rawprawns reply will be but I downloaded MSE on my sons computer about 10 days ago as he was having problems. It found no problems so downloaded Malwarebytes to try that and it found 85 objects including a number of Trojans and Malware. I have used MSE on my own computer and it was just like running Windows Defender never found a thing. I don't think I will use it on my computer again it may be free but I have my doubts about it's ability.