If you do sets like I do - based on how much you can lift explosively with perfect form, rather than trying to hit an arbitrary target each time - then 45 seconds rest is plenty. In fact that was my rest period yesterday, for dips, pullups, and hack squats at 3RM. So instead of doing 3 reps, resting 3 minutes, and doing another 3 reps, I would do 3 reps, rest 45 seconds, and do maybe 2 reps. Sometimes I had enough to do 3.
It is really interesting how differently you look at things when your target is an overall number of reps, rather than a set target of reps per set. Most plans aim for 24-25 reps, whether it's an 8x3 program or a 5x5. But this way, you are aiming for the same 25, but with more force done (because rep speed is higher) and more intensity (since rest times are lower) which is what was being discussed here in the last page or so of this thread.
Here's an article that talks a bit about this.
Here's one on lifting explosively