There are changes. I open 2000i parts and all dimensions open in LIMIT mode in Creo.
Early on (Creo 1.0) I noticed some dimensions were were flagged as changed (required regeneration) and that the dimensions changed the model to the nominal value of the limit dimensions. Meaning, that a +.005-.015 dimension may change the feature to the center of this tolerance range.
Very disturbing but I think there was a work-around for it in config.pro that does not allow this to happened.
However, having every freakin' dimension in sketches come up as limit dimensions is maddening!
As for the rest of portability, it has worked pretty well with little experience in both 2000i and WF4 imports into Creo 2.0. That is, after all, still one of PTC's strong suits.