Get this one from deal extreme:
http://www.dealextreme.com/details.dx/sku.8231
There is no reason to pay for the Canon one with the YN one around. It is cheap enough that everyone should own one as well.
I dont know which one SkipD got, but the YN one has a plug that matches the Canon one perfectly and fits nicely into the camera. The button feels pretty much just as nice as the Canon as well (maybe SLIGHTLY less tactile, I find it easy to find the half press and full press though) and functions perfectly. Only real difference is that the connector is plastic instead of metal coated on the back area, which really makes no functional difference at all (its not even the part that goes into the camera...the Canon one is plastic there as well).
Some of the other aftermarket ones are crap, the YN one is quite nice and you cant beat it for $4.80 shipped! If anything try it and see if you like it! You will not damage your camera with any of the switches as all they do is short pins on the camera. Only thing you could possibly do I guess is bend the pins on the camera if you tried to jam the connector in but you could do that with the Canon one as well.
Some of the Canon accessories are just stupidly priced, their remote switches are one of these items. It is about a 3 cent switch inside a plastic case with some wires, nothing more, nothing less. The canon might have a slightly better feel, but is it $45 more? I definitely think not.