Seeking insights on FedRAMP consultants

Respond with PM if you don't want the info public. I am doing research for a client on FedRAMP consultants. I am getting the usual sales pitches. Want to hear some "in the trenches" experiences.

Not looking at auditors, but rather companies with Fedramp platforms.

Anybody have any recommendations or warnings? I've got a bunch to consider: ProjectHosts, StackArmor, SecondFront, Paramify, etc.

Any firms to avoid?