Sucrose does not metabolize well by yeast, about 75% IIRC.
You wind up with a sweeter beer.
I do not believe that is true. Sucrose is a simple sugar and will ferment as completely as anything can.
A sucrose molecule is a glucose bound to a fructose and because of this, it is more dense than corn sugar, which is just glucose. So if you're using sucrose (which many people do regularly), keep in mind that you should use slightly less than you would if you were to use corn sugar.
The larger size of the sucrose molecule does give the yeast one extra step, that is, to break the glucose/fructose bond. For that reason, it may take a week or two longer to carbonate your beer using sucrose, but I assure you, it still works.
Many have referenced using invert sugar to prime. The invert sugar they are referring to is sucrose that has been broken into glucose and fructose. To do this, simply boil cane or beet sugar (sucrose) in water for 10 minutes prior to adding it to your beer. Some say that you need an acid catalyst to break that bond, but it is almost a consensus that a low pH will facilitate the reaction but is not necessary for this purpose.
In conclusion, buy cane sugar and boil it for 10 min before adding it to your beer.
I use
THIS site to calculate carbonation.
EDIT: I would also like to add that sucrose can be considered a superior priming sugar to dextrose because it does not readily absorb water from the air as dextrose does. The property of hygroscopy makes accurate measurement impossible with dextrose because you just don't know how many water molecules are in your sugar.