Not sure if you have already bought your impact, but I have the Mastercraft corded impact, but mine is about 4 years old and they have changed the design slightly on the newer ones. Mine has been excellent, never lacking for power, never failed to knock anything loose I've used it on. I've used it lots and it is still working great.
I also have an air impact and a cordless Mastercraft impact (also very handy, but not as much power), and normally go for the cordless for light stuff, or jump right to the corded one. Full power with no waiting for a compressor to pump up, and extension cords are just as easy to run out as air lines are.
I'm not sure if the newer design is as rugged or less rugged or what, but I strongly doubt you will wear it out under normal usage. Buy one, you won't be sorry. If it craps out, take it back. Canadian Tire is good about warrantying tools when they break, especially if it is premature failure.