Not really anything negative to say performance-wise about my 5 years of having spacers installed. Tire wear seemed to be normal on my previous set of tires, that I just sold. Balancing was never an issue. Alignment has been pretty kind to me. In fact, my alignment guy said I was in spec even after I installed new wheels&tires this past November.
I have broken a couple studs on spacers over the years. Nothing that caused any downtime. Fred Goeske (wheeladapter.com guy) sent me a few replacement studs when I contacted him, I had to pay shipping. And Spidertrax sent me a half dozen replacement studs when I called them, totally free. The broken studs were mostly my fault... torque wrench, which is now a breaker/pry bar, was badly out of cal and I snapped a lug right off into the nut once (Goekse spacer). The other time I had a similar situation during a tire rotation but the lug slightly broke free (Spidertrax spacer). Like I said though, these were easily fixed compared to replacing a lug on the hub. All I had to do was take the spacer off, put the wheel on, drive to a gas station, offer the service guy a soda, he pressed the old lug out and the new one in, drive home, remove wheel, install spacer, put the wheel back on, and presto! Done.
Turning radius hasn't been affected to the best of my knowledge. Not sure where you're coming from though. Can you explain a bit more?
I was actually anticipating buying a new pair of Spidertrax 1.25" for the rear and auctioning off my Fred Goeske 1.5" pair.