minerstat+ is an add-on to your account that you can use alongside your regular plan. With minerstat+ you will get the following add-ons.
With minerstat+ you will get access to all custom themes (hint: Hacker theme is the most popular one). You can change and test themes in Settings.
With minerstat+ you will get CSV, JSON, and SQL export options of various different historical data, which is available under Statistics > Export data.
With minerstat+ you will get historical data for 60 days instead of 14 days (as available in paying accounts).