Really? Can you make a shape then adjust it after you made it? Cause I cannot find that - as soon as I fill or stroke the vector it drops into bitmap and can only undone not adjusted.
I wrote above that Photoshop 5.0 (which GIMP was compared against) did not have vector objects, Photoshop 6.0 was the first version to have it. I'm getting a feeling that you are talking about something else here.
