I have both a Tubus Duo and a Tubus Tara. Both are great and I recommend them. The Duo is a minimalist two-piece design, and only works on forks that have braze-ons that go through the fork. The Tara will work with either type. I use the Duo on my S&S bikes, and it makes packing WAY easier since it doesn't have a hoop that goes over the wheel and easily packs flat.

Previously I used both the standard Blackburn Lowrider racks, as well as a Delta brand from Performance. I found both lacking, and they tended to slip out of alignment no matter how I adjusted them. I finally gave up and paid the Tubus price, and am happy I did.