We had the film put on our windows.
There are several different grades of window film you can choose from. All of them block heat, but not all of them block light.
We got: clear heat-blocking-shatterproof for the sidelight windows near our front door; clear heat-blocking basic film for our bedroom; medium-grade tinted for our kitchen.
There are also privacy tints that are reflective (but they only work for privacy during the day - think office buildings where you can see right in lit rooms at night), and the different grades of tint have slightly different colors, so depending on how dark you get, you wouldn't necessarily have to tint all the windows on the front of the house.
I would have it installed. We have both gone the route of DIY, and having it installed. Installation is worth it.
A lot of folks also seem to like blackout curtains or shades. Not really an option for us because I really prefer the inflow of natural light (we don't sleep terribly late here!), and because my kids and DH have dust mite allergies, and I don't want to wash or clean any more extra window treatments than I have to.