I have owned my GorillaPod for about a year now and it is brilliant. I bought a Canon EOS 400D a few months ago and it supports it just fine, but I wouldn't want to put much more weight on it. When using it anywhere other than on a flat surface, I keep hold of the camera strap just in case
If I were to get a bigger camera (eg 40D) or better/heavier lenses (L series and IS) i would upgrade to the SLR Zoom GorillaPod. I have heard of a lot of people attaching a ball head to the SLR Zoom model so that it is easier to adjust and also so they have a quick release.
I always have mine with me (attached to the side of my Slingshot 200AW like Nathan deGargoyle) and I use it a lot more than my normal tripod, because it takes no effort to carry around and it is so versatile. In fact, I recently went out with a few friends to take night time photos at the local university and only used the GorillaPod.
It is well worth the investment.