Rocket jumping isn't that hard. Aim down, jump, and shoot. Grenade jumping? That's hard, due to the grenade's erratic movement after hitting the ground and delayed timer. Sticky jumping is easy, since you control exactly where the explosion occurs, and doing it right, (dropping two stickies instead of one) you can jump clear across a map. But if you don't do it just right, you won't survive the jump. Also you'd need to get to a health pack quick, since you'll most likely have your health dropped to the teens.
Sometimes I'm thankful we Demomen lost the war, the game would have become totally broken if we got the Gunboats for ourselves.
