We have the USGA come out 2x every year. In my opinion, it isn't worth a damn if your super is even average. Every year the USGA comes out and reports that our super is doing all the right things. However, we had some issues with our greens about 2 years ago, all the while , every year getting positive reports about our course and the practices being utilized.
I know growing grass can be a tricky thing, but this wasn't a disease that happened overnight. We started using well water to irrigate our fairways, with the plan to flush out the well water before watering our greens. Well that didn't work out as well as one would have hoped. We came to find out that a few other courses with Wells had installed a separate pipe for city water to be used on the greens. our USGA representative, didn't give us that information or any other helpful tips about using our well water.
All in all, I would think it depends on the type of club that you are, we are a very high end club, that is in the top 10% of maintenance in the country both in results and budget, so the USGA isn't much help to our specific golf course. However, they may provide value for those not so high on the food chain.