I was a veterinary toxicologist for several years and had many many calls about cats sick and dead from using Hartz products.
I would not ever buy any Hartz products for any of my cats or for the shelter cats. Too many Hartz products contain permethrins which can be deadly in cats. Too many times people apply a Hartz dog product to a cat (either intentionally or by accident) and the cat will start to seizure. If a cat even has close contact with a dog that was just treated with a permethrin containing product, it can be seriously affected.
There are too many really effective and safe alternatives on the market to use this product.

Pros: Cheaper than some flea products.. but you get what you pay for

Cons: Not effective, potential toxicity

I tryed this once and it made my cat throw up. It does not work either.

Pros: none

Cons: smells strong, cats hate it, ineffective

This doesn't work. You need to buy a good brand that used to only be offered by your vet, but is now available in Petco stores.

Pros: cheap

Cons: doesn't work

This Hartz spray does not control fleas/ticks. I have used it in the past for fleas but it didn't seem to work. Frontline works better and lasts longer. We stick to Adams' flea and tick spray at the shelter.

Pros: none

Cons: harmful chemicals, doesn't work

this did not work at all ... i had always heard great things about hartz but the more and more i use this brand the more and more im disappointed

Pros: nothing

Cons: everything