We include it as a payment option on the order page for our merchants who are using Verotel. The rate on BTC is only 1% of the transaction!
The numbers really vary by merchant. It really depends on your marketing and whether or not you show your users that you do accept it. If it is only tucked away on your join pages or you leave it up to us to show on the order page, people only find out last minute and likely will not use it. We have some merchants that are pushing it and are seeing a notable amount of transactions and others don't mention it at all and see considerably less in terms of transactions.