2. One high speed CD-RW writing at 48X while watching a movie on a DVD-RAM drive, on the same cable at the same time
3. A high speed tagged queuing IBM Deskstar harddrive, doing a full image backup at the same time as watching a movie on the DVD-RAM, on the same cable as the Deskstar drive

Watching a DVD while waiting for a CDR to burn or a backup to complete is probably a valid use case.

4. One high speed CD-RW writing at 48X while dumping my entire root disk to a Deskstar drive on the same cable as the CD-RW

And burning the important data to CDR while only copying less than important stuff to disk is something I normally do quite often.

I guess the question of what is connected where means some of these things could happen together, as generally I do not reorganise my IDE devices depending on what I am doing.

This all works fairly smoothly, with only the VERY rare glitch in playback/recording

As an end user I could handle my movie briefly glitching in those sort of situations. Are the glitches with recording present of the finished copy, or is it just the process that glitches? If it is the process then I wouldn't mind, If I have data corruption then I am not happy!