I use Kayak a lot. I don't know the quality in the US, but in Europe it is working great. But, I have never installed the Kayak App, why? Because of the insane number of permissions it is requesting, like getting my unique ID, my phone number, the right to call for me, etc. This just says: "I will not respect your privacy." way better than any TOS.

OT: This is something I simply hate from the Apps in general (on Android in my case), they request way too many rights for most of them.