So far I've done about 50 miles in broad daylight with the top up and 50 miles top down. I'm perfectly happy with it. There is some reflection on the clear cover but not worse than any other car I've had. Gauges are visible and clear. I still have not used the car at night, but I expect it to be fine then too.
I did another 100 miles with the top down today. I'm definitely happy with this mod. While there is possibly more glare on the instrument panel, it's not a problem at all. No worse than either my Chevy truck or my wife's Suzuki. I think since more light reaches the face of the gauges, they are easier to read in spite of any additional glare.
Here is a pic with the top down at midday:
The old tunnels gave the effect of looking from a bright outdoor setting, through an open door to a dark room. You can't see in the room. But walk into that room and you can see fine. The eyes can't handle the bright exterior and dark interior simultaneously. The shallower tunnels reduce the contrast between light and dark making the gauge faces easier to see.
I haven't tried them at night but I expect equal to better visibility than before since they are going to be one inch closer to my eyes!