Eva eats almost all her meals from the Kong Wobbler. We both like it, she likes it because food comes out of it and I like it because it is easy to fill, easy to clean and holds an entire 1.5 cup meal of kibble no problem. I wouldn't call it difficult, but it takes 15 minutes or so to get a meal out of it and since she otherwise bolts her food down in 10-15 seconds, I think its healthier for her. Hard plastic thumps around a bit but appears basically destruction proof due to both material and shape (Eva being a dog who destroyed an extreme Kong in minutes, an extreme Kong ball and several other "guaranteed" toy in under 20 minutes). The weighted bottom means it wobbles (its in the name!) more than rolls around so its less likely to get trapped under furniture
I tried the Omega Tricky Treat. Pain the butt to load, pain in the butt to clean as its nearly impossible to get all the kibble out of it due to an interior lip that blocks the last few pieces. Not recommended at all.
Tried the larger size of the IQ treat ball. Easy enough to load, plastic didn't feel as sturdy as I would like, but mostly, it only held a tiny amount of kibble. Like 1/2 cup or less. Which might work for a small dog but was useless for feeding meals to my large dogs. Potentially worth buying for either small dogs or feeding occasional small treats like Zukes. Not worth it IMO for meals for med-large dogs.