If you decide to get one, consider two things:
1) the weight of the tube
2) how far you have to carry the tube
If you're in a situation where you can just drive up to the shore and throw the tube in, that's pretty easy. However, if you have to carry the tube any distance, you will notice a few extra pounds of tube (plus the weight of your other gear.)
My tube is an older model that weighs less than 10 pounds. (I think it's 7-8#.) Most tubes today are heavier -- as much as 13-15 pounds.