Possible incompatibility with uploadpath.
I have upload path configured to save my file attachments into subdirectories such as:
blog/YY/MM/DD/entry-name/picture1.jpg
and it also "cleans up" the file names to ensure they are unique.

Steps to reproduce:

  1. Create new node that has uploadpath and inline input format
  2. Attach a file, picture1.JPG, it will be saved as sites/all/files/picture1.JPG
  3. Save node, then re-edit
  4. The file has now been filed into a subdirectory and "cleaned up," sites/all/files/blog/08/19/node-title/picture1_JPG_283723.jpg
  5. Edit the description of the attached file to give it a good caption
  6. save the node, then re-edit
  7. insert a macro, in this case [upload|file=1]
  8. save the node, then re-edit

The macro will look like:
[upload|iid=1|file=picture1.JPG|nid=1]

Should it not say file=picture1_JPG_283723.jpg ? When the macro was created in the node, the file Picture1.JPG no longer existed. It had already been moved & saved.

Definitely not a show-stopper, but what do you think?

Oh, also the documentation for input filters needs to be updated, it still states that the tags should be [inline_upload|file=file.jpg] not [upload|file=file.jpg] Took me a bit of debugging to figure that out, lol.