I have a drop-in liner that came on my 2003 f150 and I hate it. It is almost imposible to keep clean. Worse yet, the "grooves" in the liner are almost imposible to dry after a wash. The liner is tough on the knees and everything slides around.
If you are looking for a drop-in style liner, take a look at the bedrug (
www.bedrug.com). I may opt for one of these down the road.