Rain-X can be an effective water repellent for glass shower doors, as it creates a hydrophobic barrier that causes water to bead up and slide off the glass. This can help reduce water spots, soap scum, and mineral deposits, making it easier to keep your shower door clean. However, it's important to note that Rain-X is a temporary solution and will need to be reapplied periodically, unlike the permanent protection offered by Showerguard glass.