1. Chargebacks are only necessary because of the pull nature of the US banking system. I haven't even heard about chargeback until I came to US from Europe. Bitcoin is push, no chargebacks are necessary because nobody can take your money.

2. For smaller sums of money (e.g. coffee) you can pretty much assume the transaction to be confirmed once you see it on the network. To be really, really sure the transaction is confirmed and money is yours, you have to wait about an hour.

3. Indeed, Bitcoin fluctuates, you need to peg it to your expenses which is usually your local currency. That doesn't mean you must convert it to that currency. You can incorporate this into your payment button. But yes, this is a downside.