I like the Smartline controllers. Looks like WM got it right this time.
On a side note I just got some interesting info on troubleshooting the Smartline 2-wire system:
An SL controller with dead short on 2 wire path will not stay on long enough to do any tracing/locating. One contractor came up with the idea of removing one leg of the path and connecting a solenoid to the clock and then to the wire path. Apparently there is sufficient resistance to keep the current going to do the locate.