i've found the lcd on my 5D to be very accurate, i.e. if its blur at zoom, then the image is gone-case when i download it onto my PC. but as a general rule i've learnt not to delete anything in-camera (and not to review every pic i take, only the first to confirm my settings). first of all you extend your battery life, secondly you'll never know what gems you might find when previewing on your computer screen instead of the miserable lcd, even though its the best at the moment in the dslr class. once delete, gone forever, CF cards are so cheap nowadays too...