I carry two hard Magnets as my primary putters. The beat one is the go-to disc and the fresh one is for light wind or longer throws (can be thrown harder). I also carry an unusually flat FLX Challenger that feels close to straight ESP. I simply can't abide the domey, soft, FLX challengers so if I every lose this one I'm pretty much hosed. I use the Challenger for short drives and all straightish approach shots up to the range of my Hawk.
I've tried the Focus as a replacement for the Challenger and found that they seemed sort of unpredictable and felt sort of...fast is just about the only way to put it. It was also more overstable than I'm looking for in a putter. It had great feeling plastic and I got some really nice drives with it though.