The only mention of buffer capacity I have seen is on the Chase Jarvis Blog describing the a twitter entry by one of the shooters on the video production Nikon had them create. He said he shot a burst of 10 frames 14 bit of RAW+JPG-Fine and 11 14 bit RAW but did not say the camera bogged down or make any reference to limits, other than saying both were at 6fps. Their team all seemed to be impressed with the camera. But remember they had the samples for quite a while so they were essentially Release Candidates, not out of the box final production stock. There might be some software tweaking during this period between release field testing and full scale production that is occurring now.
One thing that is apparent that us still shooters are probably underestimating is that this level of camera and the Canon 5dII/7d sales are really impacted by the video crowd. The interest in and the money spent based on number of forum posts on video production web sites and blogs is equal to or exceeds the demand by still photographers. Maybe there are just more vocal but if Nikon could better the data rate and frame rate of the Canon units, sales will explode for the mid line and pro bodies. One complaint has come up, Nikon D7000 data rates in video are 20mb/sec and the 7d is 48mb/sec. Jarvis was sure it was fast enough but there was a lot of disappointment among the bloggers and forum posters. I got the idea from reading hundreds of such posts that the video crowd cares nothing about brands or being fans, they only want tools from anywhere they can get them and would switch in a second to Nikon or even Sony if they produced what was wanted. Many mentioned their still cameras were D3s but video camera were Canon, so two sets of glass. The shoulder mounts,focus racks, steadicams and accessories that they all use dwarf the cost of the body. A cheap amateur style steadicam is $2000 but the ones they use are several times that cost apparently. There is a lot of money in the film and video production. I remember years ago wanting a large, long reach BlueBird boom stand for my music recording studio, one like I had seen in most TV and 1980 era video studios. I was used to paying a few hundred dollars for booms back then. The dealer quoted $25,000 for the BlueBird. We did get one eventually, and it was useful but I doubt it would ever pay for itself. Just 10 years before I bought my first home, a small 2 bedroom on 50 beautiful acres in the mountains for $22,000.....and it had a barn and stream as extra features to boot. Video production costs so much more than still or recording. I remember recording major records over months with production budgets of $250k, for a record that would generate $50,000,000 in sales, 12 songs. Each video, the cheapest slapped together music video, for the singles on the album would be $150,000-500,000 and take less than a week. Not sure where all the money went because the costs of cameras and editing gear was not much different, or lower than large mixing consoles and tape decks. Based on these observations, if Nikon wants to boost sales, they are going to have to create a D400 that beats the 7d and 5dII in video specs, they already have the still specs to beat them. They have to realize that how it works in real life is not as important as specs on paper to this new segment of consumer. It does not hurt Canon sales at all that they have obnoxious NR artifacts or AF that is never fixed. This crowd does not care about results, only in specs on paper. One strange thing, if you talk to young people who are spending money on such things, they all talk in buzzwords and video tech talk and relate more to moving than still photos but I hardly ever see them out actually taking video captures. I am starting to think that they really don't want to make videos as much as talk about making videos. Stan St Petersburg Russia