I've found Geocodio to be a good option too, especially if you need to do batch processing: https://www.geocod.io/
Agreed, we use them for a number of things and find them very reasonably priced (especially, unlimited plan is very good if you are doing 5+ million).
Possibly, but they only cover the US
Same here. Not using anything now, but when I needed it, they were a good value, and easy to use. They sponsored a PHP conference I went to, which is where I heard of them, and became a customer. LPT: conference sponsoring does work ;)