I have had just a few basins, no experience with Northerns. My own basins are the most docile of any of the snakes in my collection, and I have quite a few very nice snakes too.
I suppose I could handle them often, but don't do it often since they always perch right where I can watch them. I have several friends that also say basins are quite nice, and that many of the other locales can be too. Seems to be that the "trick" is to purchase captive bred babies/juvies. You can ask the disposition on them before purchase too.
If you really like the looks of them.... and they're hard to resist..... then don't write them off right away. Just wait for the right time and right snake