With a toddler, they seriously work. Here's what happened at our house two days in a row:
Suzi was playing when she got to the point where nothing was going to make her happy. For example, although she has her own little nativity set to play with, she was infuriated that I wouldn't let her play with our big one. We let her play with it last year and I spent hours searching for all the people and animals she'd squirreled away in various places around the house. This year she is allowed to play with hers, but only on the front table, and isn't allowed to touch the big Fontanini one. Anyway, she had a fit and started crying over not being allowed to hold the goat. Normally she would not throw a fit over something so small, so I knew she was tired.
"It's time for a nap," I said. A few weeks ago we would have gone upstairs to her bed at this point, and I would've tucked her in and kissed her. Much stomping and screaming would have followed. But now we've gotten a little smarter.
"Do you want to take a nap on the couch, or go upstairs to your bed?" I ask.
"Couch." Of course. And she goes right to sleep. We both get what we need, and without the power struggle which no one enjoys. It doesn't only work at naptime, though. If she is screaming for something she can't have, something dangerous like a pair of sharp scissors, I can usually say no and offer her a choice between two other fun things and she'll stop crying and pick one. If there's a food she won't eat, she'll frequently choose another healthy one if given a reasonable option.
Ahhh. It's so much easier to parent a kid you can reason with.