I have had, and have been using Kadee's 0.088" tread wheel sets for about six months. They look good -even great- and roll well, especially so in their new trucks (not surprising, perhaps!). As expected, the quality control is superb.
How the plastic/plastic journal/bearing interface will wear in the long run is not yet in evidence; but, as pointed out, it probably would not be close to a relevant issue for the vast majority of us. In any case, there would be no difference in this regard as compared to Kadee's standard wheel sets because they share the same axles.
In my rollability tests with the beautiful new Kadee Barber plain bearing trucks, both the Kadee and the Reboxx 0.088" tread replacement wheel sets (the latter with 1.020" axles) rolled only insignificantly better than the OEM standard wheel sets, not enough to make changes on that basis alone. With none of the tested wheel sets, however, did these Barber trucks roll beyond a mid-point "Acceptable/Good" level, a point just beyond half way to the "Superior" level of rollability achieved by a number of other contemporary trucks- most with replacement wheel sets.
A similar test (less the Kadee 0.088" wheel sets) with the equally new Barber S3 roller bearing trucks demonstrated about a 50% increase in rollability with Reboxx 1.025" wheel sets as compared to the OEM sets.
Denny S. Anspach MD