Does anybody have these? Do they really bloom in fall? Are they really perennial? Would they work for naturalizing in the lawn? Or would I have to pick a spot in the garden?

I don't know that they would be suitable for the lawn because you would likely need to mow it by now, and the foliage is still quite robust, has not started dying back yet. Also they may not be vigorous enough to compete with turf grass.

There are crocuses that blooms in the autumn that are real crocus, with the typical delicate blue-purple or occasionally white flowers.
https://store.brentandbeckysbulbs.com/spring/genus.php?genusid=13

In my experience, both will bloom the year they are planted.

The only autumn daffodil I could find is Sternbergia lutea, which Plant Delights Nursery lists as only being hardy to zone 7, so I don't know anything about it since it's not hardy for me.

I probably wouldn't plant fall-blooming crocus in your lawn because unlike in the spring when cold soil causes slow growth of grass, the grass is growing quickly in September and will need to be mowed when the flowers are setting buds. While they are technically perennial, the critters may eat them just like spring crocus, so in reality they rarely come back for a lot of years in my garden since the voles get them. Because I love that color in the fall, I plant them anyway, usually around plants that the voles don't like

Colchicum needs to be planted in a flower garden since the foliage is so large and coarse. They tend to be expensive per bulb, but they are toxic to critters and will multiply over time, so if you like that bright purply-pink color in the fall, I think that they are worth the money to buy a few of the less expensive ones. I bought a few and now have several very large clumps of flowers each fall after less than 10 years.

http://www2.brecks.com/topaz-autumn-daffodil/p/84637/

And here are links for the 2 Fall crocuses that Brecks sells

http://www2.brecks.com/fall-white-crocus/p/84636/

http://www2.brecks.com/fall-white-crocus/p/84636/

Maybe I'll just order 1 (I think they are all 10 bulb quantities) of each and see how they do. Will pick a spot in the garden - will forget the lawn idea.

Still looking for additional insight.

I ordered both Fall crocus (Crocus) and Autumn crocus (Colchicum) from Brent & Becky's. Colchicum are much bigger and have huge leathery leaves that come up in Spring and then die away before the flowers appear. Then the flowers come up in the Fall with no leaves. Many look like giant crocus flowers but there are some like Colchicum 'Waterlily' or 'Pleniflorum' that are double. Fall crocus are just that... crocuses that bloom in the Fall. I really enjoyed them last year; they were much smaller than Colchicum, but lovely in a group. Both kinds were shipped in late Summer and bloomed the same year in the Fall.

And I think nhbabs is right about Sternbergia lutea which does look exactly like a Fall blooming yellow crocus. White Flower farm lists it as hardy to Zone 6.

Don't expect to see any above ground growth this fall on the daffodils. They are working on growing roots now, and will put out foliage next spring. The crocus should bloom but IME they are later than ones planted in prior years.

I have the 3 groups of bulbs marked. Hopefully my patience will pay off and I will get a better show next year.