I didn't even feel sore the next day when I did 8-minute abs. I dropped out after the first 20 seconds and just laid there until the rest of the 8 minutes was up. It was way too hard.
But lets be honest, even if you have the strongest abs in the world buried under two inches of fat nobody is going to see your six pack...it will look more like a keg. If you want to work on your six pack, running on the tread mill might be more useful.
Anyway, I don't think any normal human being can actually do 8-minute abs. If you can...then you are not a normal human being...