I've been very satisfied with the "thermal" curtains my wife and I bought when we bought the house... they are not high quality, just off-the-shelf from Target, but they are white on the outside side and opaque, with the result that they reflect virtually all light back out the windows in the summer. Of course some of the heat stays in, and they don't seal around the edges, so there's room for improvement, but IMO they beat tinting the windows because we still get all the thermal gain in the winter.
I will say that our house also had very good passive solar design to begin with: no direct sunlight comes in the south-facing windows in the summer, even without the curtains, due to the eaves. But the curtains help with the indirect light.
Apparently a few years back someone went around selling thermal curtains as I have run into three from about the same time frame, but none of them knew where the curtains came from, they were just there when they purchased the home. All were sealed when closed by design, and all three of the owners were extremely pleased with their performance. Mine is a heating climate with limited need for air conditioning, but their comments included that their homes never needed ac.
I looked around at the time and nothing was available locally and what I saw on the internet needed to be custom built at a substantial cost. Been a few years, but if you have a source, I think they would be an option.
In a heating climate, sealing them is important, as thermal drapes will block the heat from the windows and can result in continued convection with increased condensation.
We were looking at the generics from Target/Walmart. They will be going in the kids rooms, so keeping costs down it important also. Glad to hear they actually work, even if they aren't sealed.