Being very good. I notice they seem to be the track of choice for upgrading the Tamiya rubber band tracks on build ups here and in magazines, etc. I bought a couple sets to use on the Tamiya T-55 and T-62 and am quite happy with them.
Having said that, I have (other) sets of Spade Ace tracks and they are pretty much just as good as Friuls. The casting on the SA tracks is of the same quality of Friuls with little or no clean up for the most part. The big difference is that while Friul typically gives you two runs of the same link to make left and right tracks, Spade Ace tracks have the holes drilled all the way through them. If you want to try to use headed pins to replicate track pins on the real tracks, you can make dedicated left and right handed tracks. The wire used by SA is also about twice as thick as Friul. I found it worked very well but was somewhat hard to cut.
These are some Spade Ace Maus tracks...
I have half a dozen set of Spade Ace tracks (Elefant, Panzer II, Maus, etc.) and they are all good IMHO.