Issues with Ticks
I tried K9 Advantix for the first time this spring. I still found fresh ticks biting my dog after one week. This never happened with Frontline. I will go back to Frontline, it always worked.

Works great
Without this stuff, the mosquitoes literally SWARM around my dog. With it, they pretty much stay away for up to 4 weeks after application. I guess it works on fleas and ticks too since she's never had any of those obnoxious parasites either. The only reason I gave it 4 instead of 5 stars is that after application, the fur can be a little matted for a couple of days. Looks kinda weird and can be dangerous to touch if you don't wash your hands right away. Side note: My dog is 68 pounds but I've been using the 55+ lb version of Advantix since she was 50 pounds. I called the company back when my dog was smaller and told them the mosquito protection wasn't working too well and they told me to go the next size up. Once I did, I didn't have any more problems. And yes, they assured me it was safe to do so in our case but I would definitely contact the company or your vet before you use more than the recommended dosage.

not sure yet
It was highly recommended by our family vet, but somehow, after we applied it on our three year old lab, he still scratchs his ears sometimes. Maybe that's just normal, we will try again after a month, and see what happens.

It works!
I've been using this on my dog for almost 5 years. She never has fleas or ticks. The only drawback is that it looks kind of bad for a few days after applying. Even though I get it down under her fur onto her skin, (she's a lab/boxer mix) there seems to be a film on her back fur that picks up dust and dirt. It also smells. And you have to wait a few days before bathing your dog. But it's worth it to not have any fleas! And never any side effects on my dog. I'm sticking with this product.

WORKS GREAT
The product works just as described. Plus it also works for fleas and mosquitos. Love it.