It depends on what sort of problems you are looking for. The person editing the article has the editor files, etc. loaded into memory, so there are no "file lock" issues. The article itself is stored in the database. The version of the article that is in the backup will be what was saved in the database at the time of the dump, not the "in process" edited version.
Similarly, an image being uploaded would be included if it was in the folder at the time the file list engine listed the files in the folder. That is a little oversimplified, but close enough.
JoomlaPack does not attempt to lock the database tables when it dumps them. If you are insanely unlucky and the article save hits at the same exact time as the dump command, then MySQL would have to play traffic cop. I'm not sure what low level locking would occur, but it could potentially affect one or both operations. It is usually assumed that a table or record lock is a temporary condition and the operation should be tried again at the database interface level.
Practically anything can happen in the real world, so yes, there could be problems. But from a statistical standpoint, you shouldn't lie awake at night worrying about them.
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