I haven't bought one of the Ottosson toys; they are rather expensive. However, Walgreens had a toy of a similar style for $9.99!
Elka is definitely a Kong veteran, and there have even been time periods where we fed her from Kongs instead of her bowls. I was interested in her reaction to the new toy. The need to slide the pieces in the puzzle is a very different approach, instead of picking up the puzzle and dropping it, or holding it down to lick it.
She brought Gumby with her to investigate. I admit, I put some food in one of the uncovered holes, so that she'd be aware that's what was going on. Food tends to be a good motivator for our girl! The puzzle is not such that I could feed her a meal with it (or I could, but I'd have to take it away and refill, and that's a little more involved than one tends to want to be when feeding one's dog from a toy).
There was a lot of sniffing. And licking.
The sliding pieces do fit in rather snugly. That, and just showing her how to do it kind of defeats the purpose, yes (that, and just showing her how to do it doesn't necessarily mean she'll get it; dogs might learn by example, but I think only to a point)?
She testified to the toy. It did not make food happen. So, she nosed the toy around on the floor for a little while as well. Overall, it kept Elka occupied for a good long time (and me too, as I was taking pictures and offering encouragement). I've had it out at least once since, on day when we had people over, but hadn't gone out for our walk. Puzzle Toy helped greatly in diminishing the mischief making so that the grownups could talk!