While there is much to be said for the previous answer, there are also places where I would take issue with it.  Mainly, it is very hard to agree with the idea that those who won the war were “not landed wealth, established gentry, and did not come from entrenched interests of power.”  If we look at the people who came to power after the Revolution, it is hard to say they were not wealthy members of the gentry.  Washington and Jefferson were wealthy plantation owners.  John Adams was from a prominent family.  Thus, the major leaders who came out of the Revolution were the same people who had been in power (at least among the colonists) before the Revolution.

To talk about the way in which the Revolution was radical, I would turn to Gordon Wood’s The Radicalism of the American Revolution.  Wood argues that the true radicalism of the Revolution came from the idea that it inspired the lower classes.  He says that the leaders of the Revolution expected that they would be the leaders of the new country.  They anticipated that the men of leisure in the new country would govern on behalf of the common people.  Wood says that the rhetoric of the Revolution helped to make this impossible.

Instead, Wood says, people came to believe that society should not be organized vertically.  There should not be any idea that some people were better than others.  What the Revolution did was to ensure that the lower classes felt that they were just as good as the people like Washington and Jefferson.  In this view, the radicalism did not really show itself completely until the US began to democratize in the early 1800s.

According to Wood, then, the radicalism of the Revolution was not about who won the Revolution but about the vision of society that the Revolution’s rhetoric imparted to the common people of the new country.

Was the American Revolution a radical or conservative event?

The answer to this question is subjective. Either answer can be adequately defended, and neither answer is more correct than the other. Additionally, "radical" and "conservative" are subjective, relative terms. What is radical for one person might not be anything close to another person's definition of radical.

Personally, I feel that anytime a group of people decides to overthrow a governing entity by using violence against that ruling power, it is quite radical. I generally consider violence to be a last resort option. The normal, "conservative," and/or political strategies have failed, and the only remaining option is violence. That's a radical step because thousands of lives would have been spared had the revolution not turned violent. America might be a very different country or maybe not independent at all, but saving lives is an admirable goal.

On the other hand, I suppose that staying passive and letting the British government dish out legislation that didn't aggressively care for the colonies could be considered the radical option. The idea of getting slapped and turning the other cheek is quite a radical idea to many people, so fighting back is the conservative option.

Was the American Revolution radical?

Different scholars have different views on this issue.  One of the most respected scholars of the Revolution, Gordon Wood, argues that the rebellion was not radical in the short term but that it was radical in the long run.  In the short term, the Revolution largely left the same people or, at the very least, the same class of people in positions of power.  This was not a radical revolution like the one in France that got rid of so many of the elites.  However, Wood argues, the Revolution brought about a huge change in social relations.  It caused people to see and to treat one another as equals instead of looking at the world in hierarchical, stratified ways.  This counts, Wood says, as a radical change.