I'm replying to this thread as a member of an independent aikido club. I am very aware of my own club's limitations and standards for testing compared with other groups who are affiliated to a larger organization.
The grading panel at the club usually consists of the head instructor and two or three other yudansha. During the test, the head instructor will call out techniques but may also ask other members of the panel if there is anything they would like to see that has not yet been shown. For yudansha, freestyle situations are asked for.
A person who is asked to test is almost guarenteed to pass as the instructor 'invites' the student to take the test knowing the student is capable. He wants to see the student perform under pressure of the testing environment. I know of only one student my instructor has failed in this manner. The student was failed not on technique but on attitude and the treatment of his uke.
We train in a Judo dojo that also supports a third japanese budo so the atmosphere is pleasant, appropriate to the art and the formality is there with the underlying intimacy of student/teacher relationships.
How does it compare to other clubs? Well, by attending seminars run by the bigger organizations I am proud to say that our 'quality control' is in place and on par with what I have seen out there.
Just a few thoughts.