Last Friday I grilled hamburgers for the family and made up a couple of burgers with ground bison just for the sh$ts and grins. 90% lean and doesn't shrink! Of course once the estrogen units found out there was bison in them thar burgers they immediately left all of them for me and would only eat their Angus cattle burgers. Like that's a big difference.
I think they're great and if the proce wasn't so damned high I'd make them a regular addition to our meals. And other than a little richer, meaty flavor they taste pretty much like regular hamburger. You just have to make sure to grill them like you would any really lean meat.
BKB