The thing that worries me is the talk that Nokia might choose not to repair/replace the device if there is sign of damage on the device.

I filed off my USB plugs before I ever inserted them, and I try to look after my N900, but it does have a few scuff marks. I have never yanked the USB lead out, or dropped it while the USB lead is plugged in, so these scuff marks are nothing to do with USB, but I worry that if I have a USB port problem in the future, Nokia might think the marks are something to do with that.