Is an antispyware really necessary?

I believe that an Anti-Virus program is enough or actually anti-spyware is most of the time just built into any anti-virus program. I have never really used an anti-spyware program. If you normally don't get any type of virus or anything after browsing the internet and you know where you are going then I wouldn't worry about anything.

I would recommend Microsoft Security Essentials. It is free and provided directly from Microsoft and have found it to pick up very well and not be too secure on false positives.

Well, your question isn't very objective, but I'll answer it anyway.

It really depends. If you are a person that downloads things quite frequently, even from a secure source, then you might still want anti-spyware. Anti-Spyware has different uses than Anti-Virus. Spyware is much harder to detect, as it doesn't really behave like a normal virus. Spyware is meant to hide behind an actual application usually, that is why programs tend to detect it even if it is legitimate.

Also, if you use your computer for storing important documents, then it might be worth the hassle.

However, I would say for average use, it is quite unnecessary. Most anti-virus has some anti-spyware anyway. I will recommend AVG Free, probably the best Security program I have found for that price.