One of these came with the house. I tried it once on some weeds last summer but was entirely unimpressed. Pulling weeds out of the loose soil by hand was way easier than using this thing on a pole.
But Layla ran across a recommendation so I busted it out again. It turns out that although it's a huge waste of time to use on weeds that can be easily pulled out of the soil (i.e., those in unpacked flower beds) it absolutely kicks ass at removing dandelions from hard-packed lawn. It's probably only takes a quarter of the time it would to pull out each weed by hand, and the success rate for pulling roots and all is well above 90%, compared to below 30% for pulling weeds by hand.
Of course, I've got about a million of those little puff-balled bastards growing in both lawns in the first place, so it'll be a while until the grass is completely clear. But at least it's way easier now.
Here in MI where the moto is "everything gets mowed", I heard the trick is mowing the d-lions while they're still flowers.
I know this because the other day when the landlord was mowing I mentioned that it was too bad he was mowing over the yellow flowers before they got a chance to puff up. To which he replied: "Gotta mow 'em before they turn. Everything gets mowed."
I find that's exactly the problem. Mowing them makes them flatten more effectively, making saucer-like weeds that cover more lawn but don't stick up very far.