Suites on Carnival are nice. You will receive priority embarkation and a larger room with nicer furnishings and a nice bathroom. The bad part is: That's about all you get for the extra money.
Unlike other lines Carnival doesn't do much in the way of full suite amenities. You get the nicer cabin and that's it.
If you want more room and a nicer looking cabin then go for it but don't expect butlers, special menus or dining venues, special treats, cocktail parties, daily canapés or other amenities that are on other lines.