Governments have already shown how they will implement tax @davebrewer (well in our country South Africa) when you bring bitcoin into the country and revert to fiat currency, profit made on purchase/sale becomes Capital Gains Tax.

Read up on the requirements for your country, they are sure to have some up already.

Government still received GST or VAT on purchases in retail no matter which currency you use, those are both taxes.

ATM's may need to be converted to transact from normal bank card swipe to include bitcoin, however I doubt that would be a massive adjustment if they really found the right people to implement changes to current technology.

The biggest obstacle is education of the people to learn more about the new blockchain technology.

If a moved to bitcoin all dealings would be on the blockchain making it unattractive to governments where dodgy deals are happening, in democratic countries this would be most interesting.