I have done it and to be quite honest I cannot sing the praises of this type of tank enough! The plant growth is superb!
To be fair I wasn't aware that the method was pioneered by D Walstad. I had come across it while looking into ways to rid my aquarium of bba which lead me to another forum that was more focused on the planted aspect of the hobby. There they recommended this method (commonly called "dirting.") with a few adjustments. I signed up and went through thread after thread reading and taking notes because although natural very few of us start out by putting organic soil into our aquarium and so I was a little apprehensive.
I must stress that I am a fish first person and until the bba took over my plants the plants themselves (although I had quite a few) were inconsequential.
The cons: After dirting your water is a little cloudy for a week.
The pros: Plant growth is far superior. Plants/dirt use up my nitrates making my reading 0ppm consistently (previously with the same fish load they'd reach anywhere from 10-20ppm a week.) Mulm (fish poop/shrimp skins etc etc) is drawn into and decomposed quickly which also replenishes the soil. Root growth is so strong that I have a visible maze of roots just below the substrate. Organic soil is far cheaper than eco complete, takishi amano's highly overpriced counter part and everything in between. I no longer have to gravel clean. My algae was reduced by 95% by the second week after dirting. I no longer need to pour nutrients/fertz into the aquarium (major win!) The fish appreciate the plant growth. I could go on and on really...
Again, I must stress that I didn't know of the Walstad method so while incorporating organic soil as the foundation of my 50gal. 98% plants and some neon tetras for decoration has never appealed to me
personally so while some aspects are the same others differ. For instance I still use my ehiem 2215 filter.
Here is a vid I made of the entire conversion process with updates on day 10 and day 27:
http://youtu.be/oEktbgHEft8
The one unforeseen problem I have is that my hair grass (e parvula) is not getting enough light because although planted at the same time as my ludwigia repens the repens has grown faster and is blocking the light.
*EDIT* one thing I should add is that with the researching I did prior I kept coming across the same point repeatedly, which is that plants absorb 40-60% more through their roots than the water column.
Op