I'd say it's about 50/50, the instructors I had that were good were great and I will remember their names and say hi to them in airports 20 years from now. They won't remember me but I don't care.

The instructors I had that weren't good/didn't give a damn were worse than useless, burning through valuable sim time. Unfortunately, almost all the PSI's/ground instructors I was exposed to were in the latter category. Bad news for anyone coming in the door today, as PSI's are now the norm (except checkrides, which are still done by the same group of airmen).

Ground school as many others have said is only attended to check the box. They will present a lot of information, similar to the CBT's, but will not "teach" you anything. I learned 80% of what you need to know from self-study, and the remaining 20% in procedures training and sims when exposed to real pilots.