To answer your question, we do work with the ACH system to load a Dwolla account, and yes, we work strictly in the US as of now.
Steps to do so:
1.) open account at https://www.dwolla.com/register.aspx NOTE: AFTER THIS, YOUR ACCOUNT CAN NOW RECEIVE DWOLLA PAYMENTS. Cool, huh? Feel free to follow @dwollaX on twitter to get a few bucks free and demo our social integration p2p feature.
2.) Verify your bank: security is obviously a top concern of ours, so we will make two small deposits into your bank account, which you will verify (this will take 2-3 business days). This is a one-time occurrence.
3.) Initiate a load to your Dwolla balance: This will take 2-3 business.
We're working with new banking products to make this process speed up exponentially, but so far, we've seen tremendous growth with Dwolla Spots and our flat 25 cent fee. Checkout our map: dwolla.com/spots.