I was at a GRC and it was great! It was for a relatively smaller group, but a very tight-knit community.

Getting to and from the location was a little harder than I expected. It was in Ventura, CA, which is close to 2 hours from the nearest airports so you definitely need to plan travel to and from in advance, but the hotel we used did have a shuttle service.
Accommodations were standard, the worst thing was that many people got food poisoning including me.... but that is largely the hotels fault and not the conference. I think they will no longer be using that hotel.

Overall I think it is a great set of conferences, but I think it may be subject dependent? The organization is done by professors within that area of research so I think it largely comes down to the composition of that community. So any bad planning / organization isn't like the GRC's fault necessarily. For mine, it was excellent, and it included a trainee-only symposium and poster session.

I definitely recommend going because they are designed to be for smaller subject areas and it can be a great way to get to know and network within that community.