No thats not what I mean / want.

Say you have a square its positioned by its top left hand corner. To enter its position you are changing the value for that corner. Say I make the centre of my page x=0. If I position my square x=0 it will be off set by its own width. However if I can tell the program that the centre of the square is its positioning tag, I can just say the squares tag x=0 and as the page centre is x=0 the square is easily centred.

Super quick.

Xara imho is the best, but it needs work in this area. If I turn on Snap and draw two spares of a random size, they dont even snap to each other unless I calculate or use a grid. Don't want to design with a grid. Its to restrictive.
Take a look at Illustrator in this area, its awesome drawing angled guides etc. Super slow redraw and calculation, but super flexible snap etc.

Unless I am missing something, in which case .. fill me in :-)