Unracking the bar should be a slide and not a lift. The bar should be at arm's length when at the tip of the rack.
Some hinges have a lip at the end, which of course has its own uses. I guess it's for safety, but I think that's accomplished just fine with a straight plug at an angle which slopes into the rack.
Anyway, the same principle applies. When the bar comes off the hooks, you should already have it at the top of the lift, or as close as possible.
The reasons for the slide-off, is that as soon as the bar comes off, it should be somewhere over your mouth/chin, which is an unstable point (the stable point is directly over your shoulders, where your arms are vertical). The slide makes sure you have that tiny bit of momentum to get it into balance with minimal effort.
If you're doing very heavy reps, and you have one of those lipped hooks, you should get your spotter to assist you with the unrack. After all, if you're doing heavy reps, the spotter should be there anyway.