Update - 14 hours
There's not much to say other than playing with this is a real pleasure and a treat. Since about the 6 hour mark, the spin has been fantastic. I'm not sure how much of it is due to the Barry Bonds-style setup, but I sure hope that when properly done most of it is still there.
Playing for the better part of an hour in moist to wet conditions 1 1/2 weeks ago has definitely reduced the mains' ability to slide back: while it's not very severe I'm now finding that I have to nudge them into place every 20 mins or so. I'm also finding that they appear to be notching faster, especially just outside the sweetspot -- so I've now put in 3 string savers. To what extent this is due to the exposure to moisture rather than natural wear is unclear to me. Possibly relevant to their longevity is the fact that under tension they look about the same thickness as the 1.18 crosses.
Other than that, they really are wonderful to play with.
String movement: minor
Spin potential: excellent to outstanding*
Arm friendlines: excellent
Fraying: virtually none
Notching: minor overall, moderate at a few intersections
Durability: keeps on truckin'
6 x Head MGPMs, 3 x Head i.PMs, Gamma X-ELS