I've always had a cover. Like others have said, I take good care of my things no matter how much they cost, and I like the convenience of a light builting with the case, just my preference.
I just switched from Kobo Touch to Sony T1 and lucked out on great deal on the official Sony case with light for $29. I love the custom fit, only reason I may change is I have nowhere for my stylus, I don't like that it doesn't stay closed via magnets or clasp, and depending how the 'shiny bezel' works for me, may change to accomodate those needs.
BTW, has anyone ever had a problem scratching the screen using the stylus? KT didn't have that, and I like using the stylus [no fingerprint smudges on screen], but am concerned about light scratches!