I haven't bought any commercial cleaners in years ever since I found out about the vinegar/detergent trick it works in the shower on my stove top, the only thing I can't seem to make myself is dish washer detergent... apparently if you use borax and washing soda (I think that was the combo I read about) it makes this white film that's hard to get off. Being a natural skeptic, I had to try it for myself... and yup! It also took a fair amount of cycles for the dish washer to stop adding the film even though only 1 cycle was done with the combo.
The good thing about the vin/detergent is you can spray in all over your shower a little while before you're going to take a shower, bring in a scrubber sponge or the like and give it a little wipe/scrub while you shower and the shower is sparkling clean upon your exit!
I used to spend AGES cleaning the shower and bathtub... now it's 2 minutes maybe.