I am an amateur at raising trees from seeds. But I did try it twenty-five years ago, not knowing if I'd have any success. I live in Washington, Pacific Northwest, Zone 7, at 1200 feet elevation. We get lots of rain in winter and spring, but little precipitation in the summer months.
I planted several walnuts (in the shell) and got one walnut tree which now produces a few walnuts each year--chipmunks get them before I do.
I planted many cherry pits and they have all produced (near as I can tell, according to the "store-bought" variety I started with). Takes about 8-10 years and a tall ladder.
I've also transplanted many fir and pine and cedar seedlings and most have thrived. Those trees tend to self-seed in my front yard.
I've tried peach pits and apricot pits, but did not have any success. I finally bought an apricot tree (two actually) and one has survived and is now bearing a few fruits on an every-other-year basis. Could be my elevation...still plenty cold when it blossoms.
I've planted any number of pear seeds and have had success with ONLY two trees (every-other-year bearers) for my many attempts. Only half of my four "store-bought" pear trees have survived, so it could also be my particular climate.
I've had several successes with varying varieties of plums. I'm the only one in my family who eats them, so I won't be planting more, though "volunteers" arise every year.
One acorn (from upstate New York) that I planted yielded a young three-foot-tall oak which (unfortunately) later got burned in a grass fire--not sure if it would have grown to maturity as they aren't native to my area.
With apple trees from seed I have been "semi-" successful. I would never say "all they are good for is firewood." I have two Red Delicious trees from seed, but the fruits tend to be smaller than store-bought apples unless I vigorously thin them early in the season. Another yummy apple tree from seed bore early and heavily, but the weight of the apples caused the main trunk to split and it has taken about 9 years for it to recover...unfortunately, it is now slowly uprooting itself (I suspect there's no taproot). Another apple tree from seed bears delicious fruit; it's my favorite, but I have no clue what variety I started with. Still other apples-from-seed turned out to be either a crabapple (glorious tree covered with blooms, and bees, every spring...prettiest tree around and it has one nice grafted branch from my "favorite" tree), OR "other" apple trees that the bugs and worms simply LOVE. I figure the bugs gotta live too, so I leave them for "Mother Nature". I don't spray, never have, never will. I prune (somewhat regularly) to allow sunlight into the crowns. I confess that I did buy one three-way apple tree (from a big-box store), but one of the varieties "took off" so that is what it primarily supplies (and I lost the tags, so I don't know/remember what they are).
I've also planted filbert nuts, but they tend to die back a lot and only the chipmunks have benefited from the trees (they're actually more like bushes--again, it could be because of my microclimate).
None of my trees are/were watered after their first year...I figured if they were meant to survive, they would because they're in the right location.
I'll also add: all my "early" tree seedlings (45-50) were started in gallon milk jugs (my five kids ensured I had a steady supply of milk jugs)...I just scissored off the top half opposite the handle--the handle being left on was handy for grabbing several containers at a time. After a couple of years, though, the plastic tends to break down because of exposure to sunlight; but I haven't found anything cheaper that supplies a goodly soil volume for young seedlings. Probably, my transplanting these seedlings after a couple of years affects their taproot.
Like I said, I have limited experience, but planting from seeds does work, even for apples. You just need a VERY long time-frame to see your successes. I've used about half an acre for all my tree-from-seed plantings (they're generally about twenty feet apart). I've recently started "planting" tree trimmings in a spot in my garden in the hopes of increasing my apple and apricot yields--time will tell if that works out. I use my apple tree produce (anywhere from 200-600 pounds/year) primarily for making applesauce--no sugar needed. I just core, slice, and cook 'em for about an hour and run them (skin and all) through a ricer. The ones with bugs/worms in them are food for the local deer and the apple cores go into the garden for "composting-in-place". The pears and cherries we eat fresh as they come into their own.
As for problems: mice girdling young trees is a problem if the snow persists too long. Did have a problem with a porcupine eating the skins off the apples while on the tree and that heavy bugger broke smaller branches as well. Porky also girdled a pair of cherry trees just beginning to produce. I found the porky in my wood pile and dispatched it...later my dog ran off its mate and that event cost me $165 to get all the quills removed at the vet. No "special" problems with critters, except deer sometimes rub their antlers and partially debark trees.
