Ask for a picture of the inside before you buy - I have some that look really similar on the outside. The inside is fine except the bottom has a punt like a champagne bottle but the diptube goes to the center, so there is still a cup or so of liquid left in the bottom after the keg kicks. It's not necessarily a problem, just something to be aware of.
As much as 8oz? Even so I would certainly buy- including that bonus punt is a clever feature. Clearly to me these tupe kegs are designed with homebrewers in mind.
I think they make nice fermenters, or if you tend to keg beer before it is totally clear, or if you naturally carbonate in kegs. I had not measured how much they retain too carefully, so I just did with one empty I have - dumped some water in, pushed it out with CO2 until it was spitting, then measured what was left. Just over 14 oz.
I agree that they are designed with homebrewers in mind, but it is obvious where cost cutting measures were used and they are just not as nice as cornies. The handles are uncomfortable when the keg is full, the punt in the middle, which is fine really, but the diptube should go down to the bottom of the edge then, not the center. Little things like that. I don't regret buying them, i just think they could be better.