Not sure how to answer the light question. The promenade runs along the interior of the ship and is totally enclosed - so other than a very small stream of light that comes from the centrum on each end, there would not be any natural light that would filter in. However, the promenade is well-lit so when your drapes are open - it would appear to be daylight.
Personally, I love to look at the ocean when sailing, but it beats an inside cabin. They are great for people watching, good vantage point for the parades and overall a good choice if you don't wish an oceanview, but may suffer claustrophobia.