I used Miracle Grow dirt last year. At the end of the season, I stuck it in totes and have been adding compost to it over the months. Also tossed in a couple cans of worms, and so far it looks like they have been doing a heckuva job. I've got some really nice, rich dirt to work with this year, and I'll supplement that with new MG dirt. I'm excited to see how it works out this year.
I like to grow some tomatoes each year in “new” dirt. I don’t have enough space in my raised beds to grow all the tomatoes I want and rotate them on a 3 year schedule.
At the end of the harvest. I dump the dirt from the buckets into the beds where I grew tomatoes, and amend it in the early spring for root crops.