I was lurking around the local dealer lot as my '04 ST was being serviced (it has the factory cover), and a older guy and his wife were looking at an '07 with a factory cover. I overheard the older guy say to the sales guy: "Do I have to get it with this cover? I think I want one I can roll-up instead?"
I fought the urge to butt in and explain the dozens of reasons why I like my factory cover:
1) It's tougher than a soft cover so I feel my "stuff" is more secure.
2) It's easy to get into, front or back.
3) It came with the vehicle and since I negotiated the price of the vehicle down to the bare paint I know I got a good deal on it.
Sure, I guess a big one-piece fiberglass might look nicer, but to me it isn't as handy.
TJR