I've used several of the canned tortoise foods. Mazuri, RepCal and currently Pretty Pets. They are made out of the usual grain products (oats, wheat, corn, soy) with added vitamins and minerals. It is convenient and it does add more fiber over a straight grocery greens diet.
But part of the fun for me is providing a varied and stimulating diet to my animals. My leopards (and russians) will sit there and eat a pile of pellets, but they seem more energized and involved in their environment when they can graze upon a variety of weeds, grasses and greens. In my yard I can find clover, dandelion, several dandelion look-alikes, wild violet, wild strawberry, plantain, henbit, at least a couple varieties of grass and several other weeds whose names I can't recall. From March until around December I can collect several of these for every meal. Lots of fiber, which is really important for my leopards. I've noticed that when I give my leopards nothing but grocery greens, their feces get very runny.
I also throw in several things from the grocery: endive (their favorite), the basic greens (collards, turnip, mustard), and a little bit of dark lettuces like red and romaine. Also, a few vegetables like carrots and squash. Sometimes I can find cactus pad (remove the spines!) which my leopards love. And I can also get hibiscus flowers and mulberry leaves from time to time.
Then around December the weeds and grasses die off (I live in Missouri) and I have to use more grocery foods. To improve the fiber content of the diet I will add some tortoise pellets along with chopped timothy hay, both soaked and then mashed together. The tortoises (both leopard and russian) like this mix. The hay boosts the fiber content and is also high in calcium.
The main drawback to the using the yard and the grocery as your food source is figuring out how to balance vitamins and minerals. I don't worry about vitamins too much because my tortoises are getting about 10 different foods a week in good weather, and at least a few hours of sunlight each week from about April to October. I sprinkle plain calcium carbonate on their food a couple times a week and also throw some cuttle bone in their enclosure.
To give my leopards more access to natural graze, I've made a rectangular frame of 1"x6" boards and covered it with a screen top. The bottom is open. I place my tortoises on a level patch of yard that has a variety of weeds and grasses and then place this frame over them. I also place a board or piece of tile over one end so there is a shady place to hide. The leopards don't dig, so they are secure, and they spend the day either grazing or napping. They get lots of sun and therefore vitamin D. I generally do this on weekends when I'm around the house.
So if you like the idea of hunting for your tortoise's food and have access to a chemical free yard, think about using weeds, grasses and greens as the main diet and pellets only when necessary.