I have never actually seen a panel totally fail. I have seen them have severe image retention, severe fading (dim picture with yellowish whites), and I have seen them overheat and damage their ribbons like LCDs do (resulting in vertical lines).
They are under vacuum (they have a little glass "nipple" on the back corner), and if they get a crack they die instantly. I smashed a screen with a line in it just to see what happens. BZZT! It usually kills the Y Board. Never buy a TV for parts that was broken while it was playing (especially if you were hoping for a good YSUS).
They are high voltage. I am not sure how high. I am sure somebody will chime in with an exact figure. I know from experience it only hurts about as much as a spark plug
