Besides Smartwool, Ibex makes merino wool glove liners also. I've tried both.

The problem I've had with wool gloves, liners or not, is that they wear out pretty quickly when worn cycling. That may change somewhat as now I am riding a fg for my winter bike instead of one with twist shifters, which I think tended to wear the gloves out prematurely.

But I like merino wool glove liners when they don't have holes in them.