After a day of using it heavily as my main browser, it was surprisingly disappointing. It is just ugly in my opinion and does not look much like the desktop counterpart. The animations became choppy in some cases and it was just slower than Safari. I was hoping more settings and possible add-ons would make this browser the best, about the same reasons as why I use it on the desktop. I could possibly see this as the best browser if I used Firefox on every platform, as it integrates Firefox sync which I found very useful. It remembers your passwords like Safari and iCloud, but I found the latter much quicker and more useful than Firefox's function. I am deeply integrated within iCloud, with hundreds of passwords and contacts that just sync between each device, which makes this browser hard to justify. I like how well it works with my history and passwords from my Windows devices, but I don't feel that it works well on iOS because of how it feels like a sandbox. It is not connected to any other service besides itself. I cannot search for links with Siri on it, define or search the page for a word, or use Open In... functions without opening in Safari first. Open in desktop mode is not an option, and it does not feel finished.
My last thoughts are that Firefox for iOS has potential, but it is too new and lacks too many essential features for me to justify switching from Safari or Chrome.