[sqrrl]

different Pentax bodies. No problems.

Pentax to panasonic, to canon, to tascam sound recorders, olympus, my 3d printer and so forth modern devices should be ok with it.

That said, if I do a paid gig I tend to blank and format my cards beforehand as they seem to write faster when the file system is clean, I also don't delete or modify files in camera. I'm not sure if you get file fragmentation on sd cards, but on someone else's coin I tend to err on the side of caution.

[pentaxus]

I once used a Sony camera that wouldn't allow me to use a card that had images from another camera brand on it. Sometimes a camera with fewer pixels won't play images from a camera that has more pixels, but the images are still there.

[mikeSF]

I believe that moving the card from one Pentax camera to another may cause the second camera to pick up the numbering sequence from the first.

Added: AstroDave beat me to it because I didn't post my reply properly; otherwise we would both have posted at about the same time.

when i've done this, it simply created a different folder in which to deposit the files, and filenames were still assigned by the camera without interrupting sequence.

[E-man]

I swap cards between cameras all the time without reformatting. I even go back and forth between my Panasonics and my Pentaxes without any problems.