is it me or does it seem like at times Firefly produces decent results and at other times it's near impossible to get something usable?

I still see variability in Firefly Version 3 Beta quality or results. For example, sometimes when rendering people you might see quite realistic results including skin and hair and other times, a person's hair may be approach a "blurry mess". It can be frustrating. I have to wonder if it comes down to how much "CPU bandwidth" is being allotted to a render at a given time. Maybe if there is a large demand on compute resources when you choose to do a render, the system just doesn't "spend as much time" on your render and you get poor results?