I've had no trouble directly related to the code 55 track with virtually no derailments and smooth operations. The track was very easy to lay and I haven't had to re-lay any track to improve operations. I did find that I had to re-gauge the wheelsets on my locos to the wide-end of the range for smooth operation over the turnouts. I've read on the web that you're better off with the wider setting anyway.

Otherwise, there were two operational problems I encountered. First was the Atlas 11° crossing, shown in the photos below. The large plastic frogs guaranteed that my VO-1000 would stall on it every time. There was no way to avoid it (except a blast of speed) as three wheelsets would inevitably lose contact with the rails. Functionally the crossing was a problem too, as I planned on using the inner track for an arrival/departure track in the yard but trains there would block access to the engine house. So I replaced the Atlas crossing with a Peco single-slip switch with metal frogs. Power to the frogs are provided by the spare contacts on the tourtise switch machines controlling the points. Of course the problem with the Peco track is tall webbing embedded in taller plastic ties, and the larger tie spacing. To connect the Peco track to the Atlas track I had to cut the bottom web off the end of the Peco rail, and "counter sink" the switch into the roadbed to get the rail heights to match up. My locos don't run as smooth over the Peco switch as the Atlas the track, but it's acceptable.