We installed Spyres on Mrs. levity's new Niner RLT. She's only tried them in dry conditions (drought here in So Cal), but so far she likes 'em. Her bike has Shimano 105 11 speed brifters (5800 model) and Yokozuna compressionless brake cable housing, and the combo gives a good firm feel with no sponginess. They seem to have plenty of stopping power for her 115 lb. using 140mm rotors. Very easy to set up and to adjust.
The mechanical Spyres are not as strong as the TRP Hy/Rd mechanical-hydraulics, but the Spyres stop and feel better than rim brakes I've tried.
Assuming each is set up properly I'd rank order them HyRd > Spyre > V-brake > cantilever.
Being a little heavier (160 lb) I went with Hy/Rd brakes and 160mm rotors. The Hy/Rd calipers are each ~50g heavier than the Spyre calipers (210g vs. 157g) and the larger rotors also weigh more, but the combo is powerful. A notch below the gold standard XT full hydraulics on my mtn bike, but plenty strong for skinny tires. Easy to lock the rear wheel from the hoods or using one finger in the drops - even nose wheelies are possible without much effort. Good feel/modulation and easy set up like the Spyres.
If you're aggressive on downhills I recommend 160mm rotors. Mine got pretty hot on a steep downhill (~500 ft drop on a 8-12% grade), but they didn't fade despite repeated hard braking at high speeds.
