It depends on the student. For me, I had particular things that interested me, so it was a great way to research and experiment - a big test. For others, it might not be so great. I certainly don't think it's for everyone, and if you don't do one you won't be missing much, imho.
I learned, though, and I'd do it again.

I went into my thesis before I was prepared to do so: it ended up being a year of hell for me. I would suggest that you do your thesis when you are ready and have a topic that you are truely interrested in that will keep you occupied for however long your thesis program is

I too went into my thesis without really knowing what I was doing. By the end of the first year I was only just starting to have any idea what I was doing.

Huge growth for me though, especially just in reading loads of stuff and in learning to write.