I had seen around the blogosphere that some people were using a mixture of dishwashing liquid and vinegar to get their tubs clean. I decided to try it. And boy does it work! Here's what you do:
1/2 cup Dawn dishwashing liquid
1/2 cup white vinegar
Put the above mixture into a spray bottle and spray down your tub/shower. Let it sit for an hour (I couldn't wait and only waited about 20 minutes) and then wipe off with a damp cleaning rag. It takes off any soap scum and hard water stains. I have to admit though if you have breathing problems you do NOT want to use this as it is very strong smelling. I turned on my bathroom vent for about an hour afterwards just to clear the air but it does work and is a lot cheaper to use than the bathroom cleaners I have tried in the past which did not work so give it a try and let me know what you think of this.
PS: Make sure you wipe your tub/shower down with water several times as this mixture can be slippery. Be clean but also be safe :)