David,
Wow, what an encouraging post!  I love the concept of synergy... I have done more, grown more, changed more and invested more in others as a part of a team that challenged me, stretched and encouraged me!

I would offer that the same underlying principle must exist in each of the four ways you suggested to create synergy (connect, shared vision, challenges &amp; control)... that principle is vulnerability.  I think for synergy to take place, we have to be willing to be vulnerable to those we partner with- transparent and open to input, challenges and yes, even criticism.

Thanks for the post!