Painfully slow - I just tried it and gave up. I know that my son's cats aren't the brightest bulbs, but I wanted proof to back it up.

And yes - some canned cat food doesn't have a pop ring - 9 Lives Tuna is one that I know of. I always wondered why canned cat tuna doesn't have this - I haven't seen any brand of it that does - and it's tuna only. Must be something to do with the processing???????