I didn't see this posted yet, but Rondo has already hit a game winner (or at least a last second shot to force overtime).
Doesn't anyone else recall the play where Pierce threw an ally-oop to Rondo who scored a layup with .5 seconds left?? It was a beautifully designed play b/c no-on expected it. If he has the ball at the end of regulation then I hope he just heads directly into the paint 
That play against Miami was amazing, but not really because of Rondo. Pierce and Doc get the majority of the credit for that play. D12 could have done the same exact thing, doesn't mean I want him taking jumpers in crunch time. That play should not even be considered when discussing him taking a last shot.
Pierce, Ray, KG (against the Knicks) and even Big Baby (against the Magic) have all taken and made game winning jumpers. I'd trust all of them before Rondo right now.
And as for Rondo heading for the paint, it depends on the situation. If they are tied or down one, fine, because he can either find an open man or get fouled. If we are down 2, he needs to let Pierce take over.