Ive used them as well.. they work great, but you can make them for cheaper just by purchasing the drip ring assemply for $15.99 and easily think of a way to duplicate their system using buckets or w/e.
What I have done is taken a black 5 gallon bucket with lid, 1 net pot slightly larger than the drip ring. Cut a hole in the lid so the net pot can fit without falling through. Punch a 1in hole in the bottom of the net pot closest to the the side, slip the drip ring assemply through, fill with hydroton, plant your little buddy, fill with water and turn on the fish pump.
GH Drip ring - $15.99
5Gallon Bucket w/lid - $5.00
Small bag of hydroton - $5.00
8-10" net pot - $2.50
Fish pump(Single) - $10.00 (Fish pump(4 outputs) - $30.00)
Nutrients - well it depends on the size of the bottle.
The single bucket setups are $59.99 they come with everything including a little bit of nutrient.. but not enough. You can find the 8 bucket packs for $250 - $350 which is a better buy of course.
My only complaint is how to flush these buckets, it can become a pain if you have a lot of them and theyre not connected. GH doesnt put a release valve on the controller or the res on the 8 pack bucket system either so you usually have to make one or spend the time dumping everything with a friend.... All in all its an easy beginner system for hydro. Cheap and effective... oh ya.. I think they use way too much hydroton than needed, I think the net pot is a perfect size and uses half the amount of hydroton.
If you can post a pic of the stem rot I can tell you if it has happened to me. I have never seen it, or at least I dont think I have.