My wife and I drove from Sydney to Hunter Valley (Pokolbin) in about 2 hours, thinking to stop for a tour and lunch at one of the wineries before continuing up the coast in our rental car. We chose McGuigan's. While it was a pretty day and the area is nice enough, it wasn't all that spectacular (at least if you've been to other well known wine producing regions) and the tour at McGuigan's wasn't much. (At $5 you get what you pay for.) they directed us to a place across the road for lunch which was tasty but nothing special, with no view and no one else around.
All in all, I think we might have been better off skipping Hunter Valley and going straight to our destination up the coast.