I've said it before and I'll say it again (and again, any time someone posts one of these threads) - I LOVE THIS TOOL!!!
I can make beads several times faster than I could without it, and it makes it super easy to get an even footprint. As for my hands and wrists, it has allowed me to keep working with glass, where I am sure I otherwise would not be able to (nerve damage in both arms from my neck, etc.).
I have the mid size and the adapter for the big hole mandrels, and the adapter works fine for the times I use it, but I don't make a ton of "fits Pandora" sized beads. The trick I found when using that size mandrel is to cut it short - like 5-6" max, so that it stays balanced evenly in the spinner and doesn't feel tippy.
As for the learning curve, it does take a bit of practice, but once you play with it a bit it will become easy. And once you see how much time you save in laying down your base bead alone, you will be in love.
I do almost everything in the spinner - even my sculptural stuff for the most part. Occasionally, I will take the mandrel out to do a few details toward the end but often I don't even have to do that.
Best.tool.evah!