...but what I really want is a half decent non auto gain external mic input, because I want to use it for documentary work.
I know that an external mic input seems like a good idea and I'd appreciate it as much as anyone. But the truth is that you want your microphone as close to the action as possible, not stuck back on the tripod or camera with you.
I use a wireless lav going into a quality recorder, a Zoom H2, a handheld mic with a built in recorder and any other tool I can get that puts the mic where the action is. Most of these will run for several hours on a set of batteries so you can put them where you want them, turn them on and capture all kinds of film without worrying about starting and stopping with every clip.
Manually syncing them up is easy but I find that I edit the audio track so much that I can't use long sync clips much anyway. A good audio track and lots of b-roll makes a better film than a talking head.
It strikes me as weird that people will haul around a camera bag filled with lenses, filters, extra this and that but believe that including a light weight high quality audio recorder is more than they want to deal with.
Just like the number of steps we're willing go through in post with D90 footage is okay but taking a few minutes to sync up high quality sound is too much trouble.
Sorry to rant on but bad sound is the easiest way to spot a cheap production while great sound is almost invisible in a high quality production. A good sound track starts with the initial capture of the audio and that almost always starts as close to the action as possible.
-a-