Actually the NEX I have is the 5n, which is roughly the same size and form factor as the black magic pocket camera.. so small, and not terribly friendly to work with.
In the right circumstances it can produce gorgeous footage, for example:
http://vimeo.com/31064478
To be honest I haven't done a whole lot with it since I bought it. Mostly I've only used it for stills.
As for the VG series, I can't really speak to those, as I've got no direct experience with them. They appear to have the same APS-C sensor as their bigger brother FS series cameras though, so I'd imagine similar, though software crippled, features to those.
I'm sure the VG's are nice cameras, but for about the same price you could get into a Canon dSLR, or the panasonic GH2 or GH3. All of which have alternate firmware options to get high bit rate recordings, etc. Sony does NOT have hacked firmware available.. It's been a work in progress for several years -- not much progress in the past year or so either.
For my money, I'd probably go with the Panasonic GH2 or GH3 at your budget level. Simply because of it's flexibility in compatible lenses (with adapters, etc).
Unless you already have a lot of Canon glass, in which case a Canon is a more logical choice.
True, the micro 4/3 has a quite large crop factor. There are options to overcome that though. Metabones Speed Booster adapters are available for micro 4/3 to several different mounts that not only boost the speed of the lens (giving you 1 full stop), but they also decrease the crop factor from 2.x to 1.42x.. In other words, your tiny micro 4/3 sensor will see the same sized image as a piece of super35mm film. (give or take a tiny amount)
The 'full frame' argument people love to throw around is really pretty bunk, in my opinion, when it comes to filmmaking. It's comparing apples to oranges.
Full frame 35mm is rather huge for a still camera because the film stock runs through the gate horizontally. Whereas with a 35mm motion picture camera, the film runs vertically. As such it's nowhere near as tall or wide as the film plane in a still camera. Thus anything beyond super35mm size is bigger than what's captured by a motion picture film camera -- unless you go up to something like a 70mm imax camera.
The bottom line, I think, is when you're buying a camera you want something that will give you the functionality you need right now. With the flexibility to grow with you for a couple of years. Given all the available options, and your budget, unless you have a bunch of canon lenses already I really think your best option right now, today would be a GH2 or a GH3. Because it's the most flexible mount system, so you could get adapters for virtually any kind of lens mount, and buy up old lenses from pawn shops, ebay, etc.. and if/when the time comes you need to to go wider and give you shallower depth of field, spend the $400-500 on a metabones adapter for your lens mount of choice.
If you already have a bunch of canon glass, get a T#i (2, 3, 4, 5..) because it has the bigger sensor, and you'll be able to use all of your existing canon lenses.
In either case, canon or panasonic -- plan on getting several fast SD cards.. don't splurge on a couple of big 64GB cards, get several smaller 16 or 32GB cards. And install the appropriate firmware hack or magic lantern, shoot in the best quality you can manage in post, and whenever possible properly light your shots, and plan them...you'll end up with beautiful footage.
