Here are some pics of my bed cover, liner, and what I use as a post hole tie down:

This pic is skewed a bit, I promise you my truck bed is not warped like the pic shows. That's an extang lo-profile bed cover with line-x bed liner. The bed cover is about a year old now and other than being dirty it works great.

Here is a pic of the inside of the bed. That's a line-x spray on bed liner. It's only 2 days old in that pic so it's still pretty clean. I had line-x on my red truck (pics of that in my gallery) and it worked great. Line-x is durable too, it stood up to a load of rocks and a metal shovel banging on it a couple times.

This is just a close up of the post hole tie-downs. I got these at walmart for $24 a pair. They're rated at 1k pounds each and help to keep the bed dry when it rains.