Yeah, it has problems.. and I/we understand it is immature.
Just sketch a 3-4 point spline (free, unconstrained) and extrude as a surface, then apply a spline on surface, then go back and drag/move the original sketch.. what happens? The spline on surface fails... well, if you do a ctrl-q it sometimes (yeah, sometimes, if you're lucky) resolves but why do you have to do a ctrl-q?? So, how can the user fix the failed spline on surface? Delete one or more the the points and hope it resolves or redo it? The whole point of relational data is to retain it or reapply/redirect the relations, no?
Why does the user have to force a rebuild? Why has it become more common with SW to force a rebuild (ctrl-q) really, why the hell does the user have to do this!?
Poor programming? (poor programming management and direction?..)
Or, more things which are incomplete and inconsistent to fulfill marketing's needs? Hey SW Corp Sales and Marketing people, you can go and suck mine, you're wasting our money and time!!
..