@blocktrades I'm replying over here due to comment depth limits and I'm replying to this...

I'm thinking about accepting checks, that would eliminate fees from credit cards and from fiat->btc fees. But we would need to add in enough lead time to make sure the check can't be cancelled (well, we could make exceptions for small amounts and good customers). But we need to add some more code on the backend to support it as well.

I'm speaking from experience here. That is a colossally bad idea.
You'd be much better going with http://www.authorize.net/solutions/merchantsolutions/merchantservices/echeck/

That way it's instant clearing and greatly reduced risks of chargebacks. Also I wouldn't even accept that unless you have the appropriate AML/KYC measures in place. Jumio is good for this.
Namaste!