On a whim, I bought a unicycle last week.
It got here on Friday, along with a book.
I spent a reasonable amount of time over the weekend just learning how to get on and off in the living room, with only a few very minor bruises. Yesterday, we went out back, and with a fence on one side and Mike on the other, I managed to actually move foward. Mostly in 10-ft chunks, but it was moving! The side-to-side balancing isn't any worse then a bike, but the front-to-back takes some getting used to. You learn forward to move forward, but the amount you learn forward is dependent on how fast you're going - too much and you fall forward, not enough and you fall backwards.
Also, there are some interesting mechanics to the actual peddling - it's easier to balance with your feet in the 9 o'clock and 3 o'clock positions, and it's much less stable at 12 and 6. So you need momentum to carry you through that position without stopping there.
This all boils down to commiting to a speed and staying there. Next weekend, I'm taking it down to the local schoolyard, where there is a very long fence (probably close to 2 city blocks?) along a sidewalk. It should be the best local place to practice - but they're closed after dark, so this time of the year it limits me to weekends only.
We'll see how the transition away from a fence goes, but right now I'm inclined to say it's not as hard as I was afraid it would be!