As another person said, what you need really depends upon what type of user you are. If you visit warez sites, porn sites, p2p sites, and the like...you probably want to invest in something a little stronger. If you don't do those types of things, you use a bit of common sense and keep up on the latest Windows patches....I'm sure the the MSE product will take care of all of your needs.
I fall into the latter category described above and plan to just use MSE. I don't really care if it's detection rate is a tad lower than something else...because I typically don't experience problems with spyware, malware and viruses anyway based on my computer usage.