In the past I have tried to clean hard water stains with the system below.
Tah-dah! The results were favorable and it did help with the stains. (see 2 pics below) However, I am still finding some stubborn stains. And quite frankly, I just don't want to make a paste every time I clean my shower. It's a long process and kinda messy.
Another product that I have used is Lime Away. It does work and I especially like it for the faucets. For shower heads, fill a plastic baggie full of the Lime Away and place faucet inside of the baggie. Secure it by wrapping the baggie with a rubber band. Let it soak then rinse. But remember to turn on the fan, open a window, wear gloves, gas mask, and your hasmat suit, whenever cleaning with this product. Holy crap the fumes!
I sprayed each product on my shower wall and faucet, scrubbed with a green scrubby and found that the Goo Gone actually worked pretty good on my faucet. The Pledge, not so much. But the Goo Gone did work better than the vinegar/baking soda paste.
Some other products and ideas that I'm dying to try are: SOS Pads (I'm a little leery of this. Afraid of the whole "scratching" thing), Oxi Clean Versatile (I love anything Oxi Clean!), WD-40 and steel wool (hmmmmm...), Cook top cleaners, Spot-X Hard Water Stain Spot Remover (see pic below. I read RAVE reviews about this product. You can purchase it at Home Depot).
Now as for my shower doors... that's another story. Stupid hard water! Stupid iron and calcium deposits!
As for my "ring around" the toilet problem, I tried EVERYTHING. Pastes, lemon juice, Lime Away, scrubbing hard, cussing, repenting for my cussing, and then praying. Nothing worked. It was the bain of my existence. I was so fearful of visitors thinking that my family had some serious intestinal issues (if you know what I mean?). Then, years ago, I overheard a lady in Deseret Book Store talking about using a pumice stone to clean her toilet bowels. "What the hay?" I had never heard of such nonsense! Using a stone to scrape your toilets clean. But I was desperate, and it was worth a try. And after much sweat and elbow grease, it worked! Now I continue to use a pumice stone on a regular basis to clean the toilets. And no longer do I worry about visitors questioning our diet (if you know what I mean.)
* tip * squirt a little liquid dish washing soap (Dawn, etc.) in your dishwasher soap dispenser and rinse deposit thing to prevent hard water stains on your dishes. But becareful if you have a water softener - this could create an excessive amount of bubbles!