My experience has been with business partners versus co-founders. I would say that complimentary skill sets can go a long way towards a successful partnership. It's fine for you and your partner to have some overlapping skills but even better if the combined skill sets cover your entire scope of work. You and your partner can divide responsibilities according to your individual strengths.
Predicting the long term outcome of a successful partnership based on personality traits is difficult even if you've know each other for years. I agree with Rob, integrity and compromise along with tolerance and work ethic are areas to consider. For example, if one partner is more extroverted, they should cover sales, marketing, investor relations, raising capital. If someone tends to be more introverted, they may be better suited to back office functions such as planning, strategizing, keeping the company organized, accounting.