Your dismissal of the problem with forks is missing a big danger to users. You say that market forces will control it, and people should just use what works best for them.
The problem is that you might guess wrong; you might look at the two forks, make your best guess as to which side is going to win out via the network effect, and put your money there. If you are wrong, and your fork dies out, there goes all your money. The market forces did their thing, and they wiped you out.
Yes, the 'users' are the ones who decide how the system develops, but that doesn't mean you as an individual user have any say; your voice will be overwhelmed by the crowd.
Of course, these risks aren't any different from the risks we face in the rest of the world. You can lose money by making the wrong choices, and your choices often get forced because of the decision of the crowd. However, we don't really face that risk using a stable national currency BECAUSE of the very things bitcoin fans tout as reasons to use bitcoin.
The reason using a currency like the US dollar is so popular is BECAUSE of the fact that the government forces everyone to accept the currency 'for all debts, public and private'. People are FORCED to accept the currency, so you can have confidence that you aren't going to be left with useless money if you accept dollars in payment. You don't have to worry about some other currency winning out as the defacto payment system, and losing all your wealth.
Of course, you have to put faith in the US government to maintain the currency, but it has a pretty strong track record of doing a fairly good job at that. I can't imagine a cryptocurrency every being able to be as stable as the dollar for hundreds of years; I mean, just look at the price volatility for bitcoins.