The problem with putting too much emphasis on retrograde planets is that all the outer planets (from Mars on out) are always retrograde when in opposition to the Sun.
For instance, when Mars reaches an aspect of trine to the Sun, ahead of it, it is very nearly time for it to "go backwards", and that retrograde motion continues until just before it is trine "behind the sun".
For each planet beyond Mars, this "switching point" happens earlier, closer and closer to square. Jupiter can trine the Sun in direct motion, but when the angle become a little wider, it is retrograde.
Saturn can only trine the Sun when it is retrograde. And this is true of Uranus, Neptune and Pluto.
A good example is grand trine coming up in April of 2008, on the 21st. The Sun at about 2 Taurus will trine Saturn at about 2 Virgo and Pluto at about 1 Capricorn. This is the only way trines to the Sun can happen.
The outer planets other than Mars are ALWAYS retrograde when trine the Sun.
So any time a person is born when the Sun is even close to opposition to several of the outer planets, there are many retrogrades. This is especially common, for obvious reasons, when the outer planets are all clustered.
One example is July 12th-July 14th, 1986. The six outer planets were all retrograde, though some just barely. But the real important part, to me, is that Mercury was retrograde then too!
(Because Mercury and Venus are so close to the Sun, you can't tell from glancing at a chart whether or not they are retrograde, so it's a much more personal matter. But you can tell the others just by the distance from the Sun.)
Another thing that is not much discussed is the speed of the direct or retrograding planets.
Certainly there is a huge difference between a planet with direct motion that will retrograde in a few days and a planet that is still retrograde but about to go direct in a few days.
A good thing to keep in mind is that any outer planet is moving close to maximum speed in retrograde motion at opposition to the Sun. So when Mars, for instance, is approaching an opposition to the Sun, it is moving backwards at about maximum speed. That means that someone born December 23rd of this year will have a "progressed Saturn" a few degrees behind the natal position at age 70.
But someone born in October of 2006, with Moon conjunct Mars, will have progressed Mars about a sign and a half ahead at about age 70.
This "colors" all the planets from Mars out. When they are very close to the Sun at birth, they progress the most. At opposition to the Sun, the actually move backwards.
This may be a large part of where the idea of "repeating lessons" comes from.
Gaer