I'm going to try it myself because it looks easier than digging up the ground and it
has a way to keep the soil moist for a while. You can also move the bucket around if
you have to.
The drawback is controlling the height of an indeterminate tomato plant which can spread over 6 feet. It makes more tomatoes spread out over a longer time than the bush determinant variety which make all their tomatoes during a shorter time period. But the bush type can stay under 4 feet.
I guess you can cut the indeterminate variety to keep it short but I'm not sure if it will hurt the plant.
I found a link to a site with directions for planting tomatoes in a 5 gallon bucket.
Here's the link with 2 videos and a list of materials needed:
Make sure the plastic is rated HDPE which is safer for using with foods.
From the website:
Here's another video on how to use aspirin to prevent tomato diseases. I'm not sure if it works but I'll give it a try: