I usually use a bit less because most recipes have waaaay too much sugar, and because it's expensive
It also has a richer flavour than sugar, so I think you can get away with less... for example, in vanilla custard I use 60g of rapadura. I buy mine bulk through a co-op so it's not as dear as the health food shop. If you need it to dissolve (eg. into liquids) grind it up first in a dry tmx bowl (sp 9, 30 seconds) - since it's granulated (not crystallised) it doesn't dissolve as quickly. I love the taste and it's so much healthier than sugar! If you haven't seen my post about rapadura, it's
here.