Some people like dirt others don't. I know some people that have had success with it to! Now personally I have tried dirt in about 4 tanks at the same time with varied results. I used Miracle Grow Organic choice dirt. The first one was a 5 gallon and it was my first planted tank. I used to much dirt and probably to much clay as well. I also used a bigger type of black gravel to cap it off. Now the plants in the tank seemed to do fairly well, especially the bannana plants and the rotalla indica. Here is a video of the tank...5 Gallon Planted Dirt Betta Tank (December 8th) (Updated) - YouTube
So it went alright, but I think due to the use of to much dirt and the large size of gravel, the dirt started to get everywhere and get all messy. It also started to smell very bad and it may have been a rotting plant or something, but I wound up re-doing it after that and then eventually taking it down and setting it up for shell dwellers
My other 2 tanks went okay, they didn't really smell or maybe a little but not as bad as the 5 gallon. One of them was a 6 gallon and it didn't have very good lighting so lots of stuff died. Also the other one was a 5 gallon hex and dwarf sag went really well in there, but some of the other stuff didn't really grow that great.
My most successful dirted tank was probably my 1.5 gallon aquarium. I know it was really small, but I used Pool Filter Sand and the dirt wasn't as big of a problem. Here it is...1.5 Gallon Nano Tank Update: March 17, 2012 - YouTube
Now it has been taken down also, not really due to dirt problems, I actually forget why to be honest; may have been a space issue! Anyways I only have 1 planted tank right now and it is a 10 gallon which I am using flourite black sand in. I think with the addition of CO2
the tank will really rock! The plants do decent with just the flourite and no ferts, but once I get CO2
the plants should do better.
In conclusion, dirt is good for some people and not for others. If you are a person who is very specific about having clean tanks it may not be the best choice. Also if you do lots of rescapes and moving plants in your tanks then it may also not be the best choice, but could still be done. I think it is good if you are on a budget and if you are dedicated to keeping the dirt under control. I think that you could probably just use a very small amount of dirt to and that would reduce the possibility of a big mess. I also recommend trying to have a plan of a scape so that when you do plant, you won't be constantly pulling them out, releasing dirt, and making a mess!
I hope I helped and good luck with the tank!
If you got any more questions feel free to ask