drinking a drink with lots of protein and calories will add weight...tons of weight gainers out there.
"ideally," you are supposed to consume as much protein in grams as your weight in lbs. eat some chicken and fish and 3 drinks a day and you should bulk a little bit.
1) I've had all the Nectar flavors, and for a period of time, I was getting all the flavors to try from Syntrax/SI103, to post my thoughts at bodybuilding.com.
2) It is well-flavored, and uses sweeteners, such as splenda, to minimize the calories within. As Nectar is a WPI (whey protein isolate), it is required to have a certain percentage of protein (normally, greater than 90%), compared to CHO's and fats. WPC (whey protein concentrate) normally contains less preotein per serving, but they carry more CHO's and fats than WPI. For that reason, WPC is cheaper.
3) The best way to explain 'weight gain' is by a simple formula:
calories in vs calories out
Now, this is very vague, I know, as not all calories are created equal. WPI/WPC's are best taken when you wake up (to minimize catabolism) as well as prior to, during, and post-workout. All other meals *should* contain real food if possible. A general rule of thumb within bodybuilding is to consume 1.5 grams of protein per pound of bodyweight.