In what form are your retirement savings? Interest accounts at banks? Your interest becomes tax free.
Mutual funds? All of the appreciation becomes tax free.
Stocks? If they are long term apprectiated you no longer owe capital gains taxes.
Real estate? No more capital gains, even on rental property.
Untaxed retirement accounts? They all become tax free.
Corporate bonds? Interest becomes tax free.
Muni bonds? Since the yield on muni's will float up to the corporate level you will lose pricipal value if you sell them before maturity. In that scenario you could be worse off. In most other scenarios you would benefit.
The tax consequences of government policy are of great concern to me, as it affects my ultimate real return greatly. It is quite enticing to a trader's mindset to obviate trading profits, I would like that - no taxes on selling, but I would not like the trading gains I've achieved to be taxed again, and then at a retroactively imposed, absurd rate, I would not like that at all. I would certainly not take the capital risks I currently take, and would withdraw from the US market in quick time. Why the hell invest in the US when emerging markets are returning at least twice the return of that in the US, albeit at a higher political risk - unless it is for safety and consistency of policy.
Should the US government impose or introduce or even threaten to employ 3rd world inconsistency on investment returns - it will ultimately achieve 3rd world results.