We use it and it did make a difference in web page performance (we tested it to confirm)
The reason it helps is because it lessens the traffic from the web server to the SQL server which is stored content as blobs in the database. For example most of the CSS and JS in a web site template is stored as blobs in the database.
You can filter what is stored in it but the key to remember is if you are heavily editing the CSS and JS in a site then you have to flush the cache to see the changes, turn it off or do the editing in a staging site (recommended)
