I've had a best partner there ever was and one that I was contemplating beating into a bloody pulp with a baseball bat. In general, based on various opinions with similar positions, I have found that partnerships work the best when there is some distance between the involved individuals. If you are close friends, it is less likely to work out. When partnering with somebody who is not as close, there is a more distant and thus more manageable relationship going on. It tends to be more respectful as you tend to be more sensitive to their needs. With close friends we just assume to know what they want or that they will go along with you. Partners that are not as close will have to communicate better and will need to compromise to keep the respect for each other. pretty sure I am not explaining this very well, but it should give you something to think about.
Dealing with another person as a partner is probably significantly lower on the importance list than having a good plan and understanding of how you will be making this business work. Additionally, if you are planning on going the distance with this endeavor, protecting your equity should be very high on your priority list. There is something to be said about bringing on the partner, but you have to understand what it will do to your future (As in 10-20 years from now) earnings.
pierre