fwiw, a roof will flex despite being made of glass or steel. In fact glass flexes a lot less. I'm not a glass expert at all but I think the torsional stability of strong laminate glass is very high. Think of glass skyscrapers with steel frames; those buildings sway a lot.

The roof rigidity would theoretically be only affected if the roof is completely open (almost becoming a convertible.) Otherwise it should be pretty solid. If you are feeling the chassis flex and the handling has become funky, then that's really another issue. I had an old Porsche Targa that acted like a squirrel on meth because the chassis twisted out after lots of miles on it (they've reinforced them over the years since.)

There may very well be even more structural rigidity built into models with panorama roofs. Total BMW had an article on racing the 5er and they used a model with a sunroof for that reason. On the E Class there's the beam inside the car that separates the two glass pieces and houses the shade rollers. That piece may also add torsional stability(?)

Engineers have plenty of design and manufacturing tools these days to allow them to offer glass roof designs without taking away any torsional rigidity. And what about the coupes with no B pillar and panorama roofs?

The Volvo XC60 (cousin to the XC90) also has a panorama roof. Again, the XC60/90 SUVs have the best roof rigidity. Manufacturers are offering pano roofs a lot now (including the new Mustang.) The BMW E61 has a pano and so does the E91.

I first thought the pano was useless and a silly extra. But I've come to appreciate it. The reality is that I don't own or drive cars worrying about what if I was in a roll over and speculate what might happen. I do have to put a certain trust into MB engineers. And if people were dying in pano roof roll overs, I think that the pano roof option would have been long gone by now in all brands.

fwiw, the noise one hears with the MB panorama is the frame; the glass floats in a frame (after all, it has to open and close.) If it were a "sealed shut" glass roof, you'd hear nothing. fwiw, mine makes noise only when I'm going over a curb or uneven surface (with less than all four wheels on that surface.) In the A4 Avant, the pano sunroof is fixed rigidly to the body by a reinforcing frame, so it makes a few squeals and groans, too.

 

I have the pano roof, and while I can certainly appreciate the pros and cons of a fixed / standard sunroof, I find that it "adds" to the driving experience. Passengers do not feel closed in with natural ambient light surrounding the cabin. Interior feels more spacious and just as quiet as the steel roof version I test drove. And BTW - zero squeaks and rattles; but we'll see over time how that progresses. I have no regrets with the pano, other than the added cost it brings to the sticker price. I do believe / hope it will help on resale value, however. Just my $.02.

 

Pano roof standard in Canada.
Zero squeaks/rattles. 4 months ownership.

 

+1, and power folding mirrors, seats memory and lot more. The only thing I'd complain though is the ergonomic of the seats... it seems impossible for me to find a perfect position to drive comfortably.

But definitely no regret at all

 

Got an E350 Luxury with P1 package and very pleased. Do not miss the features in the P2 package. Probably would have gotten the folding rear seat if I orerdered it again, but it seems a bit pricey.

 

It's a much thicker mesh on my 2014 E550. It's black and I forget that it's mesh. It dosnen't block out 100% but most of it.