To be honest, I use it mostly in a Bunco Booth type situation, so the presentation is very much as a game. It's not something that lends itself well to magic effects; much like when someone tries to tag an effect onto the end of a monte routine, the result is often less than the sum of parts.
I've heard of a few things that people have used the sets for. I know one is being used by a crossroader in the midwest, someone else bought half a dozen sets, and leaves them out as a preshow entertainment. Because they are waterproof, they lend themselves well to casual bar bets (as long as you clear that with the bar manager first, natch).
With most gambling/gaming type things (mucks, dice switches and the like), I found that these are useful at the end of gigs - that time at the end of the evening when you have finished all your tables, and you can spend some time talking to people, and maybe doing to more involved, or longer routines for the really interested folk. This is a good time to bring out something like the Spot; you can explain the game, and then just spend the next ten minutes narrating what people are doing. It's surprisingly fun, especially when the whole table wants to have a shot :)
Wulfie; when I'm up to speed, I can get close to every time (If I were to pluck an imaginary number out of my head, I'd go for a solid 95%). I honestly cannot remember if I covered this in the lesson (because I made it so long ago), but there are strategies to correct if you see that you are going to make an error. As long as you get the first two discs in the right place (and that's mainly on the first one), it's a lot easier. If you are having problems, I would bet that it's the first drop that is getting you.
I'm not here much anymore, but feel free to reach out to me on email if you would like to discuss more.