I have owned a couple of 660's in 308 and both were very good shooters, more than adequate for hunting. With that said - due to the light weight and short barrel they have signicant muzzle blast and recoil for a 308 cartridge.
They are in high demand and generally bring a premium price, they have almost reached the status of a cult item.
I don't regret selling my 308's but I had one in 243 that I do regret selling, it seemed to be about the perfect cartridge for the 660.
drover