Hi SS220,
on #1 - Those look like files that Windows Media Player (and other programs, iTunes for example) automatically download for album art to show in your player. The Pogoplug shouldn't create those in that folder. I would recheck your computer's music folder.
Can't help on #2 or #3 or #5- Sorry can't help. I don't use those devices.
#4 - Corruption of files happened quite a while ago with early firmware. I haven't had a problem for months.

Place Shifting Enthusiasts

@SS220

1) As Brandon suggests, it sounds like these files were automatically downloaded by your media applications, and you should check the source folder to see if those files are indeed there. Since those files are jpgs, though, they will automatically show up in your Photos filter along with other files recognized as supported photo file formats on Pogoplug

2) Currently, the iPad and iPhone Pogoplug apps require the thumbnails Pogoplug generates for photos in order to view those photos. Viewing photos in their original format is something we are looking into now.

3) We are aware of some stability issues with the iPhone and iPad apps and are investigating them now.

4) We take data corruption very seriously here, and do everything we can to prevent it. If you think you may have run into this, please contact support via support.pogoplug.com

5) There is a master setting that you can set to stream videos in the format you choose. The first step is to make sure the videos are transcoded

- Go to Settings -> Media Settings, select the drive on which exist the videos you want transcoded
- Set "Optimize your videos for playback" to "Auto-generate full transcode"
- Click Apply Below Changes, and then select re-scan
- Wait for your videos to complete transcoding

You can always select specific videos for transcoding by clicking "Show movies that have not been optimized for playback"

Once transcodes are available, if you want to view the transcoded version (say, outside your local network), make sure that "Optimize your videos for playback" is set to "Auto-generate full transcode" before viewing them. If you want to view them in their original format, set "Optimize your videos for playback" to "Never"before viewing them.