Advantages: You must to see.
To my understanding Stonehenge is the number one tourist site you must see in this country.
First time I saw it was on my way to Bath. It was an early morning. From a distance I already saw the stones standing there like silent people. It gave me a shock. It's so very mysterious.
If you want to give it a go, I would like to give you two tips. Hope it would be useful to you.
Stonehenge is both the national trust and the English heritage. If you are the member of one of the two organizations, you can get in Stonehenge free, your car parking is free too. Also you don't need waiting on the queue. You just need to show your card then you can get in directly. Economical both in time and money.
Better to go there earlier than later. Stonehenge is very popular. If you go there earlier than most tourists especially group ones you can save your time on the road, and you can avoid crowd when you explore it.