All the benefits of the class of travel to which you have upgraded. These include extra baggage allowances, lounge access, and chauffeur-drive, where available. (Chauffeur-drive service should be requested at least 48 hours before flight departure.)
Please note that the fare conditions of your original ticket continue to apply at all times. For example, if there are any fees or charges applicable to your original ticket, these will continue to apply even after upgrading with miles.