Pros: None - did not find it effective.
Cons: Not very effective - certainly not like the commercial; chemical; corrosive; costly for the result.
We live out in the country on a well and septic system. Our water is a little hard and does leave rust and a bit of calcium build up on surfaces over time.
I bought CLR to clear a rust stain off the tub and thought I would also run it through the washer, kettle, soak the faucet screens etc - much like the commercial on TV shows. It is septic safe so I felt alright using it sparingly to remove the build up every few months.
I followed the specifics on the label and was sorely disappointed in the results. I was expecting some bubbling and a bit of a visual cue (like the commercial!) that the CLR was removing the buildup on my items. Nothing happened. Certainly this is not an instant fix.
I ended up soaking my faucet screens overnight, then brushing them with a toothbrush to remove the loosened debris. They did look cleaner afterwards. The kettle did not look much improved after soaking over night - the calcium came off easier than the rust, but the improvement was minimal. The smell of chemical had me washing the kettle out repeatedly afterwards too. I am not keen to use this product on surfaces we use for food or drink and wont be putting it in the kettle again (even if it did work better.).
I never found a way to clean the stain in the tub with the CLR as the liquid does not stay over the stain for prolonged periods like a spray or paste would. I eventually bought a different product to clean that stain and that product worked in less than three minutes.
The bottle of CLR also has a corrosive label - so handle it carefully. I also found it had a strong chemical smell that would catch me in the throat - so I would leave the room and let the product do its work - kinda.
Overall I did not find this product worth my time or money. Vinegar was just as effective and cheaper for some of the tasks and did not put my shiny fixtures at risk.