I don't often use it, but I definitely should.  I found out my blog doesn't look so good on Safari after a rather embarrassing exchange with a co worker.  The thing about validators is that they will tell you what elements on your page don't agree with a particular browser and help you clean up your code. 

From a beginner's perspective, this could be overwhelming.  HOWEVER if you are the type of person that loves to get knee deep into coding and problem solving, you could really learn a lot from the experience. 

The first time I used it I had 28 errors in CSS and that blew my mind.  I started over and would do one thing at a time and get it right and then move to the next.

An example would be:

H1 {background-color:555;

     border-style:double;

     border-color:#000; }

Validation would tell me I did not enter a color for the Background.

I go back and put the # sign in front of my color and it validates clean.

Then I move to the next element.

This way I don't get devestated by trying to fix so many mistakes all at once.  I also learn as I go.

JB