Actually I'm quite satisfied with Jacob imprinting on Nessie.
I like him and I certainly wanted him to be happy, but not with Bella (because she OBVIOUSLY belongs to Edward!!) and that was a bit of a dilemma, because being happy for Jacob included him being with Bella (or imprint on someone, for that matter).
On the other hand I didn't want him to imprint on any girl who happens to come along. Dilemma again...
And I wanted him to be friends with Bella...
So this was probably the best outcome I could wish for - Jake is happy and in some way tied to Bella, but no longer in love with her and thus not in pain anymore. Bella happy, Jake happy, Edward happy, Nessie happy, everyone happy - excellent
(But I agree with dreamincolor - When Edward called Jake "my son" I was like "WHOA... this is so going against nature!!")