they're good for the job they were designed for. which is to reflect the light onto your plants
if you intend to put a 600w bulb in there you will have heat issues. too much heat will stress your plants. an air-cooled device such as a cooltube will help with the heat.
but if you intend to use a bulb with low wattage, that reflector will do just fine with a small extraction fan to eliminate the unwanted heat.
all depends on the size of your set-up
hope this helps