I use them. I like them.
I use Coco fiber and the granules are quite small. Normal drainage holes allow quite a bit of the coco to drain from the bottom of the container.
SmartPots keeps the media contained within. The other benefits like air pruning and excellent drainage are very nice to have as well. I simply throw mine in the washing machine after a grow and they are as new. As for the price... I spent $5 on each of my 3 gallon planters.
A fantastic system for a beginner is to purchase Six 3 gallon smartpots and a 6-pod ebb/flow expansion module. You can then fill the smart pots with any media of your choosing and either flood drain (because the fabric will readily allow the passing of the water into and out of the plant) or you can top feed and run to waste. Whatever the case is, for about $100 after shipping you have a VERY nice system capable of running any number of methods.