This is hardly definitive, but we test drove a car here in the Ft. Worth area on July 1st. it was a bit of a scorcher that day. I noted a couple of items about the pano roof:
1. Dark - So we drove two cars and both had the black headliner. Honestly, I was a bit surprised at how that impacted some of the "open feel" of the car. I sort of assumed the big pano roof would let in enough light that the dark headliner would be a non-issue. The takeaway for you here is that the glare/light seemed to be a non-issue. Indeed, my overall impression was "dark". I still prefer the look of the darker headliner overall (especially with the black or gray interior).
2. Hot to the touch, but does it matter? - Now despite what others say, the pano roof just HAS TO let more heat in than a solid roof with headliner. It is actually the latter that is the key element here. When we reached up and touched the glass it was hot (like you expect a windshield to be here in Texas). The headliner, was only warm in comparison. The pano is heavily tinted so the UV rays coming through don't bake everything they hit (unlike the windshield). It will, however, RADIATE some small amount of heat. Neither my wife or I found it objectionable, however. Indeed, pre-cooling the car for even a minute or so likely negates any heat concerns overall.
This was just two back to back test drives so take it all with a grain of salt.