I've tried a few but I think they are a little less hardy than Grevilleas. I had B. saxicola for a while and it froze to the ground almost every winter, it finally pooped out totally after 4-5 yeras. I planted B. serrata and it died, but I will try again. I started a lot of B. serrata and B. robur for my nursery so I will be trying those out. I also started B. canei but they are still small seedlings. That is supposed to be one of the hardiest ones, as I'm sure you are aware. Another one that should be really hardy is B. meisneri, but it is not that showy. Other than that I think the best way to get some hardy Banksias is go down to Australia and try to find populations of them at high altitudes. I also know Brian in Bremerton has B. integrifolia (or is it marginata.... I get those two mixed up) and there is a garden on Vashon Island with a few Banksias as well.