I've also never used any of the straps that come with my cameras; their only purpose is to advertise the brand and model.
When I see people using them, I really can't fathom why - they're unbelievably uncomfortable, scratchy against your skin and just really bad at balancing the weight of the camera and lens.
I use one of the women's Black Rapid straps. Best strap ever for me.
Well I for one use them and I have had no issues, yet. I would like a Black Rapid set for my cameras, but right now I do not have the money to spare and the Canon ones do me just fine. It is a matter of preference, I for one think the Canon strap is quite comfortable, well for me at least.