This wireless remote is not a genuine Canon item, but is produced by YONGNUO Digital, sold by BV electronics.
It arrived very promptly, and was well packaged, but didn't work.
It doesn't come with any operating instructions, so after re-reading the Camera Operating instructions which detail how to use it, I decided to replace the battery.
It had arrived with a CR-2025 Lithium Cell fitted, even though the battery compartment is marked up for it to be fitted with a CR-2032. They are the same diameter and voltage, but the CR-2025 is much thinner so possibly wasn't making proper contact. I then noticed the date code on the CR-2025 that it had shipped with was 03/10, which I assume means March 2010, so it's already 4 months past it's expiry date, so maybe dead.
Having fitted a new CR-2032, it then worked fine.
It seems good for the price, and if it had worked out of the box would have had 5 stars.