Reviving a zombie thread as it seems like the only one dedicated to the RSI Smartcap.
I have one on my F350. Recently used it on a road trip to AZ. I can confirm that mine also survived a heavy downpour with no leaks. I think some water came in the vent when I drove it through a high pressure car wash but not much and it was all just below the vent. The build quality seems great and I love the side access. I had a fiberglass shell a while back on a GMC Sierra for reference. I got the all metal sides, (no side windows) as they seem unnecessary and it has a cool metal rack in place of where the windows would be.
I think they did a good job balancing weight and strength as it feels solid but not heavy. All the doors open and close easily.
As for the negatives, I waited almost a year for mine and I think it was about $1k more than an equivalent fiberglass shell. Also, on my road trip to AZ, the inside turned into an oven. The metal was almost too hot to touch. Of course outside air temp was about 115 but fiberglass definitely would have insulated better. I'm thinking about adding a white vinyl wrap to the roof where it can't be seen from the sides.