Yes. The attic absorbs a great deal of heat from the sun during the summer and becomes much hotter than the rest of the house. The better your attic is insulated, the less this heat build-up will affect the temperature of the house. Venting the attic replaces this heated attic air with air of the normal outdoor temperature, and this can greatly cool an overheated house. Good gravity ventilation will do a lot, roof-top power ventilators or central exhaust fans will do more. In fact, they can often be the only summer "air conditioning" a house needs, and certainly they are more economical than conventional air conditioning.
All the problems associated with vents in the attic apply only during winter. In the summer the house is dryer than the air outside, and you cannot create condensation problems in the attic during the summer with power attic vents.
You may have heard that even if you already have an air conditioner, an attic vent will help to reduce the load on it by cooling the attic. The catch is that the more insulation you have in the attic, the less effect a power vent will have on the temperature in the house. Studies from the states show that by the time you get R-32 of insulation in the attic, the savings on air conditioning costs are less than the cost of running the attic fan. By now almost all houses in Canada have at least R-32 in the attic, so the argument for power attic vents is not