I've tried this! And I loved the results. The "reservoir system" is my favorite hydro technique for a few reasons. I just found this rollitup website, and upon coming here, the first thing I wanted to do is see how many others use this system. Considering how easy, effective, and inexpensive this setup is, I'm very, very surprised that nobody on this massive forum talks about using it.
I started growing pot about 15 years ago, before the www took off, so all I was armed with was High Times magazine and Rosenthal's book - Marijuana Grower's Handbook. Ed's book may seem a bit outdated now, but it still provides a lot of very useful information. In about half of a page, it briefly mentions those two "passive hydroponics" techniques. I wanted to try it out and see how it worked.
The results were great, and the advantages are numerous, I'll try list them here:
1. VERY inexpensive setup, so no need to buy overpriced hydro stuff from a specialized hydro shop
2. The small amount of soil you can use in your potting mix will provide all of the micronutrients required by the plants, so you can use cheap, but effective, MiracleGro for the macro nutes, selling at about $7 for a bucket of it... you'll never run out.
3. The plants determine how much water they need, so that takes out all of the guess work required for some of the other techniques.
4. The soil acts a PH/nute buffer, which makes it difficult to mess up, like all the other more finicky hydro systems. Perfect for beginners.
5. The plants can grow like mad, like any other hydro system, since you still disolve nutes directly into the water.
6. No other system is this low maintenance. Just refill the reservoir when needed.
Bottom line is, they grew amazingly with no nute burn, over or under watering, etc. It was just a very easy, low-maintenance, and very effective hydro method that is very difficult to get wrong. I'm hooked on this, and I'm putting together a new grow closet that will do this, and I may post a journal on this site providing details to encourage all others to try it out.
If you want more info on the particulars of my setup, feel free to ask.