As far as I can tell, these places tend to have fairly steep immigration/visa hurdles to overcome, usually involving some kind of employer sponsorship (presumably to deter freeloaders?).
If anyone here has done this, I'd love to hear your stories.
First, where you're going. You obviously want to go somewhere with better healthcare than the U.S., which isn't all that difficult to find. The ? becomes what your obligations will be as a somewhat permanent resident and how you can maintain that status legally. That's really going to be location dependent, but you should look and look hard before you leap, because the consequences could be unpleasant if you screw up. I believe there are agencies that cater to potential expats like yourself, and if you're really serious about this you should talk to one of them to make sure you don't step on any landmines in the process.
As for the second ?, The US assumes that you continue to owe US taxes as long as you maintain your citizenship, and they make it difficult to give that up. I don't know exact figures, but you are exempt up to something like $78000 of income and are allowed to write any foreign taxes you pay on that off, but as long as you are a US citizen you're on the hook. If you move to Singapore and strike it rich, unless you pay the IRS you could have extradition hearings in your future. I'm pretty sure the deficient US health care system would be pretty low on your list of worries in that case. Again, this is the sort of thing a professional could tell you more about, but this is definitely out there. I don't want to advocate giving up your citizenship lightly, but know that the US is unique in this sort of taxation and making a fortune abroad without paying US taxes would almost certainly be viewed as some sort of tax evasion if you didn't proceed very carefully.
Furthermore, at that point, you will most likely be able to shelter your income anyway by putting it into a corporation, and you shouldn't be worried about striking it rich abroad.
Once you shelter into a corporation, how do you un-shelter? Assumption being that you do want to spend a little of it. You can pay it yourself via salary, or dividends. However, from income tax perspective it's all income anyways.
Note that the "free health care" only covers doctor and hospital visits/procedures. It does not cover dental, optical, or any medications. Like in the US, any Canadian employer will offer a benefits plan to cover these things, or you can purchase insurance for them on your own.
This is a trade-off though. There is not much of a startup scene in Canada. The few "major" tech centers are really weak compared to most US cities. There is not much innovation. How many tech startups can you think of that came out of Canada? They do exist, but the deck is clearly stacked against them. On the other hand, there is less competition for funding, so maybe you can use that as an advantage. I am sure you have read the PG article about why your city matters.
I've lived in both countries, and people in both get a "grass is greener" viewpoint (aside from the too-proud patriots on either side). It is easier to see the things you don't have and want, rather than the things that you do have and would miss.
My personal opinion is that the US is more extreme in all directions. Higher highs and lower lows. Crazier crazies. Except weather. Canada is cold :) But it depends what you want to do, and what will best cater to your needs.
I hate the health care system here, would love to be under the UK National Health Care system instead, but overall would rather be living in SF than UK.
I suck up the $200/month health insurance (I'm a healthy 29 year old). If I had kids it would be a different story, mind you.
If you want to see if you qualify for immigration to Canada as a skilled worker, http://www.cic.gc.ca/english/immigrate/skilled/assess/index.... has an online test. (I just took the test for the hell of it, and I qualified, even though I don’t have a Canadian job offer in hand and je parle français comme une vache espagnole.)