I absolutely love the concept of eternal marriage and the sealing of the family of God - and I also love the concept that everyone can be part of that, regardless of their religious affiliation in this life. I understand the emphasis on temple marriage and sealings, but I also believe God will not "put assunder" ANY couple that truly becomes one in this life - that the sealing ordinances are important symbolically but only shadows of what I would call true practical sealing.
A couple can be "temple sealed" without being "truly sealed" - and a couple can be "truly sealed" without being "temple sealed". Frankly, that actually is taught and understood in the Church (even if not as explicitly as I would like), so it doesn't cause me any real angst. Also, frankly, that concept is not taught explicitly in any other Christian denomination (at least, not in the same way as in the LDS Church) - and it's an ideal I believe desperately needs to be taught and internalized by humanity.
Finally, there is a power in taking a symbol and "actualizing" it through a physical performance that includes BOTH body and spirit. The same is true of something like baptism, where there is a tangible event that is "recorded in the body", if you will. I want eternal marriage to be something "embodied" in an ordinance - even as I would like the rhetoric ratcheted down a notch with regard to non-temple marriages (especially of non-Mormons) and the concept divorced more directly from the other temple requirements. (pun intended)