Hi,

Presently, xmr.to is great when you need to pay someone. The receiver expects a certain amount of bitcoins.

Another use case, that I recently used, is when I just want to send bitcoins anonymously and I don't have amount requirements. Here, it is painful to have to calculate the amount of BTC. The person just want to get the bitcoins and doesn't care about the exact amount. In that situation, removing the need to enter a bitcoin amount (and to calculate it) would help. UI-wise, I propose a simple checkbox called "no precise amount" next to "enter amount in bitcoins".