I don't think I have until a friend mentioned it to me recently when I complained about my writing and using words like "great" all the time!
So now instead of using the same words all the time I always have my thesaurus open on my computer so I can quickly check if I want to use another word -I also bought a hard copy of a thesaurus however find the internet one a lot quicker.
At least with all this modern technology, we should cut down less trees!
Oh absolutely !!! I was never apart from mine during secondary school and university. Excellent if you want to expand your vocabulary. I would use them all the time when writing essays at school, to find similar words. No one wants to repeat themselves. I started using dictionaries when reading, from about grade 6, in case there was a word I had never heard of, or didn't understand. The teacher didn't even suggest it, I did it of my own volition. Helped to expand my vocabulary.
I use the thesaurus on the internet all the time. I also have one on my bookshelf right next to a big dictionary. I received both as a Christmas gift when I was about 15 - even as a 15 year old I was STOKED to get such an awesome gift!