Whether or not "love" is enough has been a question I wrestled with in the past w/ktspktsp (right around last Christmas, actually), because I saw us as having so many differences that no matter how much we loved each other, we couldn't sacrifice those things that made us who we are, just for the sake of a relationship. That's how I felt then... that we were drifting towards incompatibility, even while loving each other deeply.
As we talk more about possibly getting married, I find myself whittling down to the highest two levels of Maslow's needs. Spirituality (do both people have to have a similar spirituality?), and self-realization (do both people have similiar life goals that can be fulfilled in the same geographical place?)... these things cannot be mediated by love alone, unless extraordinary compromise of the self is to happen. And that I see as being unhealthy.
We've worked through everything else up to those points, but for me these are the things that love in itself cannot conquer because it comes down to two completely independent individuals with different backgrounds and beliefs. The question of how we would raise our children is also involved in these discussions... can we compromise effectively, and raise children on a solid, unified foundation? Both of us are still questioning these higher-needs topics for ourselves (spirituality and life-goals aren't set in stone for either of us yet), so they haven't become exclusive-izing categories... and I hope that they don't. But I guess I always leave room for that, at least until we have worked through them thoroughly and have "graduated" to engagement.