Strong points of Wing Chun:
1. Wing Chun fighters can often develop into good defensive fighters, counter-strikers, and "scientific"/technical Kick-Boxers.
However, it requires the Wing Chun fighter to have a Jeet Kune Do type mindset, where they give up on traditionalism. They use what's useful, and throw out what's not working.
2. Wing Chun fighters can develop into devastating close range strikers, where punches and kicks hit at unexpectedly close range.
Wing Chun teaches how to strike without needing space, no "John Wayne" wind up punches, etc... Very efficient and direct striking.
However, in a MMA environment, it requires the Wing Chun fighter to give up the traditional stance. The stance and body posture must be modified so that its merged and is a quasi Boxing stance.
A bad habit of some Wing Chun fighters is punching for speed or the gimmicky "chain punching". In MMA, POWER COUNTS. Rapid punching is fine, but you need to put your body weight into it. When Wing Chun fighters modify their stance and use a semi-Boxing stance, many will find they can put more weight into their punches, but still also do it from close range.
3. Wing Chun fighters have a devastating blind side rush attack, that can be very effective.
Many Wing Chun fighters are taught to close the distance rapidly and get an angle behind the elbow of the opponent's lead hand. In this way you can strike with 2 hands, but he has only 1 hand to defend himself and its hard to get out of the way.
This can be an effective technique whether in Boxing, Kick-Boxing, or MMA.
4. Wing Chun fighters have very effective ways of checking and stopping kicks.
A not widely known secret is that Wing Chun stop kicks are even more advanced than Muay Thai leg checking. Combining the techniques make for some great kick defense.
Even more, Wing Chun has some nice unorthodox leg attacks and trips.
Just like Machida Karate, the trick is to adapt Wing Chun to MMA and blend its techniques with Kick-Boxing and Submission/Catch-Wrestling.