I'm not sure why there is so much negative sentiment about this effect. Rumble can be used pretty nicely for a range of things, for example if you attempt to click on something which should not allow focus, or if you add an item to a new item to a page which would otherwise look too similar to the rest of the page and you want to draw attention to it ... there are loads of valid uses for this.
It would be pretty great for replicating OS X's "shaking no" effect when you type your password in wrong on the login screen (it needs a falloff setting though).
Only downside here is that the slower rumbling just makes it look jerky and cheap - it appears to have the same animation, just with large gaps between the frames, instead of adding a little bit of easing.
edit: Now I realize what vibe it was giving me... the 200-speed one makes me feel like I'm watching South Park.
