Iridium vs ShapeShifter

[epochblue]

I recently installed Iridium, and while everything is working just fine, I do have a question:

I know ShapeShifter skins "on-the-fly," right? Iridium is a bit more invasive, that is, what exactly does Iridium change? And because it's more invasive, would I notice the kinds of slow-downs I would otherwise notice with a ShapeShifter-like skinning app, correct?

More than that - is there a case to be made for not installing Iridum (I mean, is there potential for irrepairable damage to my system?)

Thanks for the help!