Anyone integrated with Avalara?

I'm building an ecommerce system that aggregates sellers and I'm
looking to automate the tax compliance. Since we have people buying
from every state, and potentially selling from any state, we can't
just keep up on our local tax codes, we need to be up on everyone's.

It looks like we'll have to go with a system like Avalara, and I was
just wondering if anyone had worked with them and what their
experience has been. Specifically using Ruby to talk with their API.