I bought a couple to use in Calgary (ONLY for Banff / Jasper Fairmonts). There were more restrictions on the certs than on the packaging and I promptly returned them.

As I recall, there were very specific dates they could be used, and they could only be applied to base room-only rates (so no packages, promotions, etc.). They might be OK if you're going on a straight-up room without a package deal?

Nelson