If you have serious buildup to deal with, you'll probably need something like CLR to get it off. Once you've done that, I highly recommend the vinegar/Dawn mixture to keep it sparkling clean. I also accidentally found out that a purifying shampoo (cheap, like Suave works perfectly) removes soap scum. Again, it's got to be done regularly to make it easy. We have clear glass shower doors that the sun shines on, so anything on them looks awful. Although they get dried after every use, it's pretty gross how much soap and hard water buildup shows up.