Hi Diederik,
Have you planned to do anything about this matter ?
I was working on bug 168651 (tiled clones in transformed groups) and
found it quite a hassle to find what was going on in which coordinate
system for the center.
I also found a bug related to the new unit stuff (when in a non-px
document, a transformation center is wrongly computed for tiled clones)
--
Mc