On my Ti 400 Rev A, there was minimal chipping.
On my Ti 550 Rev B, there was outrageous chipping.
On my Ti 800 Rev C, a small amount of chipping on the back hinges occured after several months.
All of these units had a few chips incurred by my own carelessness, in addition to the ones that happened 'by themselves'.
I skipped the Rev D 1Ghz for a 17", so I don't know about chipping on the final revision of Titanium.