From my observations of Venus in Scorpio, it can result in a distrustful nature in love, quite suspicious of the other's intentions and much probing and analysis of the other has to be done before any sort of commitment is made. However, if the Scorpio Venus person does decide to let the other in, it can often result in highly intense, deep bonds on a soul level. The Scorpio Venus person is going to be highly selective about the other's they closely relate to, and not on a superficial basis; they are not so concerned with worldly achievements of the other as they are with soul and emotional purity and intentions. The high side of this placement is a very pure, deep and meaningful bond, but the low side may result in jealousy, extremes and overbearing attachment. It really depends on how the native handles the placement, as well as the overall placement of Venus by aspect/midpoint. The first meeting chart (and it's transits to both native's charts) will also reveal much about how Venus will function, and the composite and progressed synastry charts should also be observed for further clues.
Venus could be considered uncomfortable in this place, as it is traditionally in "detriment", yet it is possible for Venus to maintain a healthy expression in Scorpio. Relationships may take on a highly sexual tone, and certainly the Scorpio Venus person isn't going to get into frivolous or casual relations unless they personally experience power and control issues. If the partner is up for the intensity, and can gain the respect of the Scorpio Venus native, certainly things could be quite interesting. An other with a strong Pluto placement may also especially appreciate the other's Scorpio Venus, as Plutonians bear the intensity Venus in Scorpio admires.
Sharing of resources on all levels becomes very important to Scorpio Venus people, including internal (soul/sexual) and external (physical/monetary) resources. The Scorpio Venus native requires clear and honest communication in all areas of sharing and partnership, and detests any attempts to hide or obfuscate intentions.
Emotions run high with Venus in Scorpio, as water (Scorpio is fixed water) rules the emotional being. There is also often a degree of inflexibility, due to Scorpio's fixed nature. Sometimes this manifests in the native taking the relationship too seriously or personally, lacking detachment, and/or an "all or nothing" attitude towards relating in general. They tend to make extreme sacrifices for love, but only if they truly believe the other is worth it. For those relating to a Scorpio Venus native, it is best to realize and observe just how much the native may sacrifice for them, and show appreciation and understanding of the other's willingness to do so, and be sure the other doesn't ever get into a state of feeling used or abused by ensuring they don't cause the other to take unnecessary sacrifices leading to a less than mutual feeling from either side.
These natives tend to be preoccupied with the underlying psychology of those they relate to, and how their internal mental and emotional processes work. Don't be surprised if these natives want to probe your inner workings, and realize that shutting them out of your inner self will be equivalent to pushing them away.
Also be aware these natives may use sex or shared resources as a power tactic, "attachment entrapment", or method of control, yet those who handle this placement in a higher-functioning manner will have either transmuted this possibility or never expressed it in the first place.
The above words on Mars and Scorpio are quite well put, better than I could do, and one should remember that Mars rules Aries and Scorpio on the classical zodiac, so from a classical standpoint Mars is at home in Scorpio.
With the relating planets paired in signs, they may "click" very well, especially at first, but the lack of differences may create a slump later on down the line as the energies will be similar. Often times, we relate very well to people of similar energies, but lack the dynamic interaction to perpetuate the experience. However, one should take the whole of the chart into consideration, as there may be other highly dynamic and exciting placements which will constitute this part of the relationship. If that was to be the case, these sign-conjunct placements may constitute the similar ground on which the other dynamic interaction finds its "base" -- We all need a healthy combination of similarities and differences to perpetuate a healthy and meaningful relationship.
In consideration of the wide-of-conjunct but both-in-Scorpio placement first mentioned, you might consider the ruling planet of the decanates and dwads of Scorpio in question. These two planets will exhibit a further dispositorship of these natal objects, further affecting the planet's interaction. Decanates and dwads don't exhibit a really strong influence, but an influence none the less, and should be considered to extract more meaning from the placements
Of course I havn't seen the whole chart, but i would agree this is an interesting setup and will likely encourage some strong attraction between the two in question. Don't forget to look for close-orbed squares or oppositions between naturally at-odds planets, which can cause real troubles in relationships through strong and hard-to-resolve differences, and you might also check out the Sun/Moon and Venus/Mars midpoints to add some additional detail to the analysis. I also find the Lunar nodes to be very telling of relationship connections, as they often point to the karmic meaning of the relationship.