I can ride my Road Bike, Full Suspension MTB, Hardtail MTB, and Hybrid all without hands without problems on paths, smooth trails, roads, etc. My Focus hybird is super-stable, I could ride for miles if I had to. I was riding with my buddy on his old steel Schwinn Hardtail on a railtrail one day and I rode no-hands for a period of time to grab a snack and some water. He tried and could NOT let his hand off the bars. So, when we took a break, we switched bikes. I rode his Schwinn without hands for half a mile, he could not let go of the bars on my Focus. So I'd say it takes some getting used to riding without hands, and some people have the innate ability, and some do not.

By the way, I can wheelie any of my bikes also.... many people have a problem with that, too.