It all depends on what environment you are backpacking in. Mountain terrain has never been great for living off the land. Tropics and coastal areas are much easier.

I fish and fly gear weighs so little (about half a pound) that I think it is well worth the effort. Of course, you have to learn the skill first. Fish is a supplement - not all your calories.

Berries are very seasonal. You can only get sufficient berries to make a difference when they are harvestable - usually late season. Same with roots - seasonal.

I usually can get enough wild greens to have a salad. Again not for calories, but for a nice variety and the vitamin C. Columbines are my favorite - just love to eat these beautiful flowers. Anothe is Miner's Lettuce. And Elk Thistle.

As for mushrooms, I only eat a few kinds that I am very sure of and in areas that I have been before.

All in all - it is just something to add a bit of variety and keep me busy. But I do appriciate that I know enough to get some food if I need to in a survival situation.

The more valuable experience is simply to spend 4 days in the woods without food and walk out 40 miles and learn how you phycologically handle it. I have done this several times. I learned that energy depletes fast - make as many miles as you can the first two days. After about 3 days I tend to halucinate. You really have to concentrate to keep your head. Training does help. With training you do not panic.