Started playing mixed about 3 years ago. Have to admit it took 2 seasons just to start to get handle on all the "Mars vs. Venus" dynamics at play in a match. Then another 2 seasons to begin to fully understand them. Figure another 2-3 seasons and I may actually be on the winning side of a reasonable number of matches
My observations to date are in line with what many of you have stated:
1. The weaker player determines the outcome. Either they are attacked constantly and can not respond, or their partner presses to hard and ends up with way too many double faults and unforced errors. This can be extremely frustrating for the stronger partner and lead to abnormal behavior on their part.
2. A weak serve is punished fiercely. So is the player stupid enough to be at the net when said serve is hit.
3. If the weaker player can consistently get service returns and volleys back in play, good things happen. If they can just hit their serves deep, no matter how soft, then get the resulting return back over the net a high percentage of the time, you win.
4. Having the same partner over and over really helps.
5. Women have an incredibly high tolerance for male ego-centric behavior.
6. Being polite to both your partner and the woman on the other team seems to surprise everyone on the court. Can't count the number of times the woman on the other side of the net has expressed surprise when I complement her for playing a great game/match or for hitting a great shot that torches us.
7. If you take it too seriously, its a miserable experience for everyone on the court.
So to answer the original question, match players as close in ability as is possible and let them play together frequently.
Mixed presents a whole different set of challenges from men's doubles and thats what makes it fun. Maybe its a better pursuit for the person who focuses on the journey, not the outcome.