Actually I have. And it still looks like a horrible design.

 

C&D slammed the XLR for exactly that reason. They tested it in the fall, and guess what happened when they went to open the hatch... Yup! Interior hosed.

EDIT: it was the trunk interior C&D complained about not the actual interior. so either I originally read that wrong or my memory got twisted in the 2 years since... bottom of third paragraph. but that's still horrible design either way.

 

Like I said, it is certainly not ideal, but I don't see it as a huge problem (and neither do buyers, it seems).

1) All folding hardtops that have the trunk share space with the top will allow the trunk/ luggage to get wet if you drop the top when it is covered in water (after a fresh rain). Perhaps you get more water in the XLR (water from the decklid and the roof itself, vs. just the roof), but all will do it.

2) All will allow water to get in if the top is already down and a rainstorm comes, causing you to put the top UP while it is raining. Hell, that could come down to the angle at which the rain is falling, etc.

3) Even a traditional softtop, whose top does not go in the trunk, will still allow water into the top stowage area if you put the top down while it is wet. In my Miata, I'll occasionally drop the top while it is wet (from morning condensation, for example). Some water will then make its way onto the parcel shelf, which is part of the interior, not the trunk, in that car. It dries.

4) Dropping the top while it is covered in fresh rainwater (or condensation) can be avoided in any of these cars by simply driving for a mile or two to blow the standing water off. Problem solved.

I guess I don't see the big deal here, since it is a problem common to one degree or another in any droptop. I mean, I don't think it would be the deciding factor for most people. What it will come down to is, which car do you like better? If someone prefers the stealth fighter styling and conservative but rich interior of the XLR, along with its sportier roots and lighter-on-its-feet feel, I doubt the top alone is going to push them into a much more expensive SL. If someone likes the more elegant styling and the carved from a solid billet, heavier GT feel of the SL500 (or just wants a 3 pointed star), they will go that route and enjoy its fancier, quicker to operate folding top.