OK, here is the roll call for my fleet:

Volvos: six 740/940 cars all using Dexcool for up to eight years continuously. The ONLY failure experienced was in one replacement Nissen brass-solder radiator, which failed after one year. The replacement Volvo OEM aluminum unit in that car has lasted three years with no problems. My conclusion is that for B230 engines using mixed iron/aluminum components, Dexcool and distilled water work just fine.

GM cars: three A-series Pontiacs using Dexcool for up to six years. No abnormal failures, but a little more leaking from seals, etc. was experienced. These engines and cooling systems are mixed iron/aluminum.

Anecdotal Evidence for Volvo 6200 series five/six cylinder all-aluminum engines: Dexcool is not a good choice; Volvo C or another silicated coolant works better.

Conclusions: if you have a brass/solder radiator, don't use Dexcool. If you have an all-aluminum Volvo engine, don't use Dexcool. Aside from these two exceptions, it works great.