I think that these formulas are pretty decent rules of thumb -- in other words, if you use this little formula and have a 71, you're probably not going. On the other hand, it's important to remember that these are NOT formulas that the adcoms use, so they're not actually relavant to whether or not you are going to get in, just whether or not you've got a decent shot. I wouldn't worry if you're a little below that magic 95 number, nor should you see a 110 and feel like you have guaranteed admission.
Also, one thing that these formulas leave out is disqualifying grade points or scores. For example, someone could conceivably have a 4.0 in cumulative and science GPAs, a 15 on the MCAT, and have a 95. That person is probably still not going to (allopathic US) med school in this application cycle. On the other side, someone could have a 35 MCAT, a 3.5 science, and a 2.5 cumulative, and I wouldn't say that they've got a great shot, either.
The point is, those formulas can be useful for telling you whether you're in the ballpark, but don't feel like they will keep you out or get you in.