At the time I bought the SUT with the bed cover, I wasn't convinced the cover was a good idea. One road trip is all it took to prove it's a terrific thing to have. Like others said, it keeps contents dry, it's sturdy and it has a reasonably secure locking system on it.
After reading your question about removing and re-installing, I had a closer look at the mounting. IMO, you'll have to have a darned good reason to want to do that. It's not a complicated intall but then again, it's not something you'll want to do for a quick trip to the hardware store.
The good news is, the lid raises to a high enough vertical angle that you can likely put your mother-in-law back there in a rocking chair even with the lid on. (If she talks back, ditch the chair and close the lid -- she'll fit.
)
The Hummer bed mat is thick, fits perfectly and has drain holes. I haven't seen an after market product that fits
exactly but there's probably one out there that fits okay and will work. The Hummer brand mat isn't too costly and it
definitely matches the overall theme of the truck.