Ive run BB7's and Spykes(same as Spyre but with MTB cable pull).
They both brake well but I swapped the Spykes for BB7's mainly because I couldn't get them stop squealing when warm,like Brucey,I felt the detents on the adjusting screws weren't positive enough.
I was also familiar with BB7's on three other bikes one of those a tandem that we'd toured on and found to be excellent brakes.
IME Steve76's concerns are unfounded,the concave/convex washers and elongated slots in the calipers don't cause any problems with the caliper running skewed to the rotor,in fact quite the opposite(below I've written how I set BB7's from scratch)
I've never had a problem with the reaction arm returning to it's stop and releasing pads from the rotor to their set/adjusted position,and can confirm what Bruce's posted that the ts-ing is caused by an out of true rotor(my straighting procedure is also below).
There is definitely no problem with there being one fixed pad and one free,it doesn't affect braking in the slightest and is just as good the two moving pads on the Spyke/Spyre brakes.
The only fault I can find to with BB7's is that they stick out past the frame and fork veerryyy slightly,which in practice isn't a problem at all.
Set up for BB7's is a simple procedure to produce optimum braking and even pad wear:-
First slack off the caliper screws to the frame or adapter brackets until you can juusssttt wobble the caliper on the convex/concave washer assembleys and the caliper can be moved in and out on the elongated slots.
Next screw in both pad adjusters until they grip the rotor as if the the brake was on,but with the rotor in the centre of the caliper slot(Avid advise the rotor to be more to the moving pad side but I find that doesn't matter)
Now with the pads gripping the rotor tighten the previously slackened caliper bolts.
Next back off each adjuster equally until the wheel runs freely and there's an equal gap either side of the rotor.
Then and only then attach the cable to the reaction arm pulling on the free end of the cable with pliers but being careful not to disturb the reaction arm from is stop.
Try the brake by pulling hard on the lever and setting the cable outer in its stops,this may produce slack in the inner cable,take slack out by slacking off the pinch bolt and pulling any slack out of the inner as previously.
Check If the wheel still runs free,if so s check if you can get another click out of either adjuster without the rotor rubbing.If the rotors rubbing the pads back off a click,and check if the reaction arm is on it's stop and not being held of by the cable,it'd it is slack off the pinch bolt so the the arm goes to It's stop then retighten the pinch bolt.
The job is done for fitting.
Now ride the bike down the muckiest grittiest lane or track you can find and if necessary throw some sand and water on the caliper and pads then do some hard braking.This will bed the pads in PDQ
I prefer sintered pads as supplied with new BB7's as they last much longer than Organics.
If you have the ts-ing of an out of true rotor it's probably,unless really bent,within 0.75mm,and can be sraightened in situ with a small adjustable spanner by slowly turning to wheel to find where it's rubbing and on which pad.
The find the nearest rotor spoke,clamp the adjustable spanner onto it and gently ease it in the direction you want it to go until the rotor is straight,true and not rubbing.
NOTE:- this is a gentle and careful procedure that needs a leettle finesse,not a hamfisted grunt of a job,and needs a leettle practice to get the feel of.
Whatever you do,don't be tempted to try straightening the rotor by bending the rotor with the adjustable spanner clamped over the braking surface as this could buckle or kink the rotor's braking surface and make matters worse.
My 2d's worth