Folks, I've just successfully completed another file transfer via the USB Cable (which was my original intent), but it has had some, er, interesting side-effects, so first let me enumerate my environment: I use 2012.08 Maint. Release with KDE-4 and LXDE installed. I am doing all this from LXDE.
I think I may have been right about ~/media (read that: "your home directory"/media) being a poor choice for this. I created a folder called ~/000_USB/Nexus_7, and issued the appropriate mount command from the shell:
[goofy@localhost ~]$ mtpfs ~/000_USB/Nexus_7
This gained me access to the folders on the tablet. I opened PCManFM to access them, but it froze. I wound up having to end the process with CTRL-ALT-ESC, and started Dolphin, since it usually runs well enough in LXDE. It was very slow, but finally accessed the folder. I transferred two large files (videos) to the Movies folder on the tablet and this took a long time, with Dolphin messaging about "unable to change permissions" on the files...
Unmounting the tablet:
[goofy@localhost ~]$ fusermount -u ~/000_USB/Nexus_7
enabled me to successfully detach the tablet from the USB cable. The files are where they should be, and are accessible by the apps I use to play back video.
I don't have time to play with this too much more right now - I'm on my way to work in just a few. I'll pick this back up on Monday.
Airdroid is hit and miss for me because of a wifi issue with my laptop since the 2012 upgrade that I'll tackle later - I've seen this before and can't remember what I had to do to make it work (frakkin' Broadcom wifi adapter! grrr!)
More when I know it, folks.