This is my third year using them. In addition to helping keep the soil moist (particularly helpful for baskets in full sun), they also help to keep the soil from getting too compacted.

I plan to use them this year for the first time. I have added them into my pots already, but haven't noticed a huge difference in the amount of times I need to water.

Meh.

I do not use straight potting mix in my planters, I mix peat or potting soil with quality top soil. This cuts down a lot on frequency of watering. Straight potting soil dries out seemingly every day, I just don't have time to water that much. Mixing in top soil helps tremendously with water retention. So the crystals didn't really do much in my case other than hurt my pocketbook (they're expensive).

I have used the crystals when planting shrubbery, though, in areas where the soil is on the dry side (hydrangeas under maples aren't the easiest to keep moist....) and for that I think they are well worth it.

They crystals last years in the soil, great for permanent plantings, worth the expense. Not worth it for pottery where the most of the soil gets discarded at teh end of every season (well, mine does, anyway, I get good masses of roots in there).