There have been a few (2?) reports of the e-ink screen fading in long exposure to direct sunlight as the display heats above its operating temperature range. I have not duplicated this exercise and in several hours of reading in direct sunlight the display stayed easy to read with great contrast.
The unit is not waterproof -- far from it with the number of buttons and connector slots (power, USB, headphone, cradle, and SD/Memory Stick slot.) Some have used a plastic sandwich bag around the Reader while reading in the tub. They report that they are well pleased with the experience.
Several people have cracked their screens from putting the Reader in their backpack or otherwise exposing it to situations that put pressure on the front of the unit. The expense to repair the screen is almost equal to a new Reader so if possible, get the insurance offered by SonyStyle for the Reader as it is (as I remember) about $54 for a couple of years.
Bulldozer? I don't think so.