Hi,
Nikon in video is the same as Pentax. In short, another mess. Then getting another
at least 3000 euros (welcome to the new world order) on accessories like: mate box on rail, external lcd, follow focus, batteries, ext mic and arm etc...and you have something usable, and you look like Robocop.(ahh dslrs). It takes at least 5min to put all that in working order.
Something that made me laugh, I phones the Zacuto's dealer in Madrid and asked for an external LCD I've been recommend, so the guy was saying that I had logically to ad another what they call "magic arm" or magic something. From a 500 euros lcd, adding the battery and magical support the bill jumps to more than 1000 euros taxes included. I really like those marketing guys with their magic bills really.
In Nikkors (I don't know to wich extend the Nikon's bodies have a compatibility with vintage manual lenses), the vintage pearls work brillantly and probably shoot 720.
There are no other options in terms of frame rate and you are stucked to a limited range of parameters, like with Pentax. And I've heard that this Nikon has a prob with live view, not allowing to change properlly the aperture once live view is on. Or it's a hoax or Nikon is kidding because that would be a serious issue.
Edit:
It's confirmed that with the D7000, aperture is not adjustable when you are in Live view and manual mode. Don't know if when in video you recuperate the function while filming. But what a stupid implementation from Nikon! sure they will fix that in a firware soon.
I think gwhitf that if you want a superfast access to video with the traditional shutter button, it really goes against what those cameras can do because just putting the machinery in combat order with all the accessory's saga is slower than a turtle, but that's my 2$ thought. The irony is that, thinking the same as you, many users claimed that a dedicated button would make sense and manufacturers are implementing it, yes...it would in the case that you can use the traditional shutter to shoot stills (jump to) when you are in the video process and I'm not sure the D7000 can do that.
Changing my optics (I avoid using zooms, not for purist but simply because I have a range of MF primes from a time where photography was...well, a craft?) with that mess seems more like a meditation process than anything else. So in all that slowness, direct access to this or that is just not going to help anything, unless you just want to do candid's videos and be ready for the unexpected, as you said if your camera is setted to video permanently, using the normal shutter button makes sense, being the most natural for the old foxes.
The new kids will love this dedicated (red ?) button.
I'm afraid your dream of a Nikon's dedicated video camera really usable is not today. Same as Canon and Pentax. As I pointed here, I think the only way is building accessories or invest on bigger artillery like the Red and problem solved. If I had the incomes to do that today (and the needs) I won't hesitate.
Here is a good place to start for chasing the precious accessories, usefull link (India has its goodies too in this crisis economy):
http://www.thecinecity.com/eshop/home.phpThey are serious.
Good luck and good video shooting.
Fred.