My experience at Barbacoa was at their Shin Marunouchi Building location. The price was 5800yen for their Churrasco all-you-can-eat dinner.
This is probably one of the best places to go for meat even including all the amazing yakiniku places. The meat here is much closer to American style steaks, not so marbled, crisper on the outside and slightly tougher. Like yakiniku, you get a lot of different selections of meat based on parts, cooking style, and also what animal. Everything tastes amazing and you truly get all that you can eat. Oh, and surprisingly, the salad bar is pretty good as well.
The restaurant is also very fun, while pretty upscale. Gigantic chunks of meat are brought to the table and cut right in front of you. Sometimes they bring a little model of a cow and point out where in the cow you are eating. What's also great about the Shin Maru location is the view. Overlook the Imperial Palace, the Diet building, and even see Mt. Fuji on really clear days.
This is a great place to go when you're craving meat and also when you need a nice, but not too stiff place to take someone.