I have mixed feelings about the clamshell doors on my 58 Burb. I have always loved the look of the clamshell and it was an important factor in my decision to buy the one I did.
As has been stated, they are much cooler than the barn doors.
That being said, two significant drawbacks I have noticed are visibility and ease of access. Being tall (6'4") I have a hard time seeing out the back window. With the crown of the roof and the window being set about 4-6 inches from the top of the lift gate, I can't see directly out the back. Using the rear view mirror I can only see about 100-150 feet behind me. It's safe enough to drive but you can't see the cops approaching from a long way off. :-) I'm seriously considering buying a dash mounted rear view mirror like in the old corvettes. I think that would help alot.
The other issue is ease of access. It is true that you can open just the lift gate and put stuff in the back behind the rear seat. That is ok for groceries and other light stuff. If you need to get something big/heavy into/out of the back you have to drop the tailgate. Since the lower half is about half again as tall as a standard truck tailgate, you either have to bend way over from the side or back or you have to climb up on the tailgate to get into the back of the truck. With the hard steel tailgate, that is not a comfortable process. Barn doors alow the convenience of being able to step right up to the bumber and put something right in the bed.
Bottom line is I'm not going to change the doors since I already sold off the barn doors that came originally and I think the clamshell is cool. That being said I often wish for the convenience of the barn doors.
There has been talk and I believe someone may have posted about combining the two. Using the upper lift gate and cut down lower doors or a split tailgate. You'd have to install an extra set of hinges on the lower half but it could be done.
