Repairs are easier to hide and the canoes tend to be very resistant to abrasion. Fiberglass is not very resistant to shock, and a hull slammed up against rocks can crack. The outer materials are sensitive to sunlight and require indoor storage. Fiberglass composite may be an excellent alternative to Royalex or Kevlar for whitewater. In it's pure form, it is best suited for limited use in flat water.
Weight can vary from manufacturer and the composite blend used.
If you are new to buying canoes, fiberglass is a difficult material to decide upon, and has a lot of variables. Just because a canoe is lightweight, does not mean it is high quality. Make sure to ask a lot of questions when considering a fiberglass canoe, and if you plan to whitewater, make sure to get a durable composite material. Lightweight, wood, canvas, cedar strip, and birch bark canoes paddle like a dream, and will draw a lot of attention where ever you go. There hulls can be damaged very easily, and some designs require buoyancy chambers.