I have mixed views on the Kong Wobbler. The Amazon reviews are really favorable, but I have a little different experience. Don't get me wrong, it's a really fun and well made toy. The problem is...it's super annoying when my dog is playing with it.
I have a 80 pound Rhodesian Ridgeback who LOVES food. He goes after this thing like it's nobody's business. He bats it around mercilessly into every table, chair, lamp, and nook and cranny he can. It is LOUD. It also ends up in places he can't get to it, so I have to pull it out from under the bed or behind doors...everywhere. Not only loud, it also will ding up your table legs if you have fragile items.
Is it challenging?
My dog doesn't have a problem getting all the food out. Sometimes it seems too easy, so I just take a piece of scotch tape and put it over part of the hole. He's gotten a little smarter and starts to peel off the tape, but it works for the most part to prolong the task.
Overall, it's a really cool toy but I find myself not wanting to use it much. If you have a basement or garage or outside area where you will use it, I highly recommend it. It's a fun toy for your dog and will keep him entertained. It's also good for dogs who eat too fast. It's worth it if you know the downsides up front. No one seemed to mention it on Amazon.